EP1247015B1 - Method for warming-up an internal combustion engine - Google Patents

Description

State of the art

The invention relates to a method for warming up an internal combustion engine, in particular of a motor vehicle, in which fuel is injected into an intake pipe or into a combustion chamber, and in which a warm-up factor for increasing the injected fuel quantity is determined below an operating temperature of the internal combustion engine. The invention also relates to a corresponding internal combustion engine and to a corresponding control unit for such an internal combustion engine.

Such a method, such an internal combustion engine and such a control unit are for example of a so-called intake manifold injection such as US-A-4,711,217 known. There, fuel is injected in a homogeneous operation during the intake in the intake manifold of the internal combustion engine, to then be sucked into the combustion chamber of the same. Accordingly, in so-called direct-injection internal combustion engines, the fuel is injected directly into the combustion chamber during the intake phase or during the compression phase and burned there.

When warming up an increased amount of fuel in the non-operationally warm engine in the Intake pipe or are injected into the combustion chamber. This is known to be carried out with the aid of a warm-up factor, which influences the fuel quantity to be injected below the operating temperature of the internal combustion engine.

The known determination of the warm-up factor is based on intake manifold injections and thus can not be used flexibly. In particular, the known determination of the warm-up factor can be used only conditionally for direct-injection internal combustion engines.

Purpose and advantages of the invention

The object of the invention is to provide a method for warming up an internal combustion engine with which a greater flexibility and in particular a simplified application with simultaneously improved warm-up behavior of the internal combustion engine can be achieved.

This object is achieved in a method of the type mentioned in the present invention that the warm-up factor is determined from a basic factor and a load-dependent factor. In an internal combustion engine and a control unit of the type mentioned, the object is achieved according to the invention.

Due to the separation according to the invention of the basic factor and the load-dependent factor, the latter factor can be determined for different operating modes independently of the basic factor. For a simple use of the determination of the warm-up factor according to the invention in direct-injection internal combustion engines is possible.

It is also possible by the separation according to the invention to apply the basic factor and the load-dependent factor independently. The same applies to the determination of the load-dependent factor in the different operating modes of a direct-injection internal combustion engine.

In particular, it is not necessary in the invention to subsequently change the determination of the basic factor as a function of a load applied to the internal combustion engine.

Due to the achievable flexibility of the invention, the invention is also readily applicable to intake manifold injections. Here, above all, the independent application of the basic factor and the load-dependent factor is advantageously noticeable.

In advantageous developments of the invention, the load-dependent factor is determined as a function of an integrated air mass and / or an integrated fuel mass and / or engine temperature of the internal combustion engine and / or the load-dependent factor as a function of a relative air charge and / or a relative amount of fuel and / or an actual or desired lambda and / or an actual or desired torque of the internal combustion engine.

It is essential that the load-dependent factor reacts as quickly and flexibly to load changes of the internal combustion engine and / or other changes in operating variables of the internal combustion engine. This then results in the advantage of a subjectively good "drivability" of the internal combustion engine even at low operating temperature.

In a further advantageous embodiment of the invention, the basic factor is determined as a function of the engine temperature. This represents a particularly simple, but nevertheless sufficient possibility for determining the basic factor.

In an advantageous embodiment of the invention, the load-dependent factor and the basic factor are additively linked together. Thus, the present invention independently determined factors are summarized again to the warm-up factor.

In an advantageous embodiment of the invention, the load-dependent factor or the sum of the load-dependent factor and the basic factor as a function of the speed of the internal combustion engine is weighted. The weighting thus influences either the load-dependent factor alone or the sum of the load-dependent factor and the basic factor. Thus, it is possible to make corresponding adjustments with regard to the rotational speed weighting, depending on the type of internal combustion engine.

Of particular importance is the realization of the method according to the invention in the form of a control element which is provided for a control unit of an internal combustion engine, in particular of a motor vehicle. In this case, a program is stored on the control, which is executable on a computing device, in particular on a microprocessor, and suitable for carrying out the method according to the invention. In this case, therefore, the invention is realized by a program stored on the control program, so that this provided with the program control in the same way is the invention as the method to whose execution the program is suitable. As a control In particular, an electrical storage medium can be used, for example a read-only memory or a flash memory.

Other features, applications and advantages of the invention will become apparent from the following description of embodiments of the invention, which are illustrated in the figures of the drawing. All described or illustrated features, alone or in any combination form the subject matter of the invention, regardless of their summary in the claims or their dependency and regardless of their formulation or representation in the description or in the drawing.

Embodiments of the invention

FIG. 1

shows a schematic block diagram of an embodiment of an internal combustion engine according to the invention, and

FIG. 2

shows a schematic flow diagram of a method according to the invention for warming up the internal combustion engine of FIG. 1 ,

In the FIG. 1 an internal combustion engine 1 of a motor vehicle is shown, in which a piston 2 in a cylinder 3 back and forth. The cylinder 3 is provided with a combustion chamber 4, which is limited inter alia by the piston 2, an inlet valve 5 and an outlet valve 6. With the intake valve 5 is an intake pipe 7 and with the exhaust valve 6, an exhaust pipe 8 is coupled.

In the region of the intake valve 5 and the exhaust valve 6, an injection valve 9 and a spark plug 10 protrude into the combustion chamber 4. About the injection valve 9 can fuel in the combustion chamber 4 are injected. With the spark plug 10, the fuel in the combustion chamber 4 can be ignited.

In the intake pipe 7, a rotatable throttle valve 11 is housed, via which the intake pipe 7 air can be supplied. The amount of air supplied is dependent on the angular position of the throttle valve 11. In the exhaust pipe 8, a catalyst 12 is housed, which serves to purify the exhaust gases resulting from the combustion of the fuel.

From the exhaust pipe 8, an exhaust gas recirculation pipe 13 leads back to the intake pipe 7. In the exhaust gas recirculation pipe 13, an exhaust gas recirculation valve 14 is housed, with which the amount of recirculated into the intake pipe 7 exhaust gas can be adjusted. The exhaust gas recirculation pipe 13 and the exhaust gas recirculation valve 14 form a so-called exhaust gas recirculation.

From a fuel tank 15, a tank vent line 16 leads to the intake pipe 7. In the tank vent line 16, a tank vent valve 17 is housed, with which the amount of fuel vapor supplied to the intake pipe 7 from the fuel tank 15 is adjustable. The tank vent line 16 and the tank vent valve 17 form a so-called tank vent.

The piston 2 is set by the combustion of the fuel in the combustion chamber 4 in a reciprocating motion, which is transmitted to a non-illustrated crankshaft and exerts on this torque.

A control unit 18 is acted upon by input signals 19, which represent operating variables of the internal combustion engine 1 measured by means of sensors. For example, that is Control unit 18 with an air mass sensor, a lambda sensor, a speed sensor and the like connected. Furthermore, the controller 18 is connected to an accelerator pedal sensor which generates a signal indicative of the position of a driver-operable accelerator pedal and thus the requested torque. The control unit 18 generates output signals 20 with which the behavior of the internal combustion engine 1 can be influenced via actuators or actuators. For example, the controller 18 is connected to the injection valve 9, the spark plug 10 and the throttle valve 11 and the like, and generates the signals required for driving them.

Among other things, the control unit 18 is provided to control the operating variables of the internal combustion engine 1 and / or to regulate. For example, the fuel mass injected by the injection valve 9 into the combustion chamber 4 is controlled and / or regulated by the control unit 18, in particular with regard to low fuel consumption and / or low pollutant development. For this purpose, the control unit 18 is provided with a microprocessor which has stored in a storage medium, in particular in a flash memory, a program which is adapted to perform said control and / or regulation.

The internal combustion engine 1 of FIG. 1 can be operated in a plurality of modes. Thus, it is possible to operate the internal combustion engine 1 in a homogeneous operation, a stratified operation, a homogeneous lean operation, a double injection operation and the like.

In homogeneous operation, the fuel is injected during the intake phase of the injection valve 9 directly into the combustion chamber 4 of the internal combustion engine 1. The fuel is thus still largely until ignition swirled, so that in the combustion chamber 4, a substantially homogeneous fuel / air mixture is formed. The moment to be generated is set essentially by the position of the throttle valve 11 by the control unit 18. In homogeneous operation, the operating variables of the internal combustion engine 1 are controlled and / or regulated such that lambda is equal to one. Homogenous operation is used in particular at full load.

The homogeneous lean operation largely corresponds to the homogeneous operation, but the lambda is set to a value greater than one.

In stratified operation, the fuel is injected during the compression phase of the injection valve 9 directly into the combustion chamber 4 of the internal combustion engine 1. Thus, in the ignition by the spark plug 10 no homogeneous mixture in the combustion chamber 4 is present, but a fuel stratification. The throttle valve 11 may, except for requirements e.g. the exhaust gas recirculation and / or the tank ventilation, fully open and the internal combustion engine 1 are operated with it throttled. The torque to be generated is largely set in shift operation via the fuel mass. With the shift operation, the internal combustion engine 1 can be operated in particular at idle and at partial load.

Between the above modes of the internal combustion engine 1 can be switched back and forth or. Such switches are performed by the controller 18.

If the internal combustion engine 1 is started at a temperature which is below an operating temperature of the internal combustion engine 1, the internal combustion engine 1 is started, for example, at low outside temperatures after a long standstill, the injected into the combustion chamber 4 Fuel quantity increased. In this way, not only an ignitable air / fuel mixture in the combustion chamber 4 is provided, but also those losses of fuel are compensated by the entry of fuel into the engine oil and / or by building a wall film of fuel in Combustion chamber 4 arise.

By each combustion, the internal combustion engine 1 is heated, so that the increase in the amount of fuel can be slowly withdrawn. If the operating temperature of the internal combustion engine 1 is reached, the injected fuel quantity is no longer increased, at least insofar.

The increase in the amount of fuel injected during the cold start of the internal combustion engine 1 and its slow withdrawal is performed by the controller 18 with the aid of a warm-up factor fWL. This warm-up factor fWL can also be linked multiplicatively with a so-called post-start factor in order then to influence the quantity of fuel to be injected into the combustion chamber 4.

In the FIG. 2 the determination of the warm-up factor fWL is shown. The warm-up factor fWL is determined from a basic factor fG and a load-dependent factor fLA. Thus, a distinction is made between a substantially idle-only factor, the basic factor fG, and a factor occurring only under load, the load-dependent factor fLA. The basic factor fG and the load-dependent factor fLA are thus independent of each other and can be applied separately.

The basic factor fG is determined by means of an idling map 10 to which an engine start temperature TMS and a motor temperature TM are input. By the idling map 10, the basic factor fG is so set to give a desired lambda curve for the idle or a small applied load.

The engine start temperature TMS is that temperature of the internal combustion engine 1 that has this at startup. This distinguishes between different starting strategies for a restart in cold outside temperatures and a restart in warm but not operationally warm internal combustion engine. Engine temperature TM is the current engine temperature that increases with each combustion. When starting the internal combustion engine 1, engine start temperature TMS and engine temperature TM are the same for at least a short time.

To determine the load-dependent factor fLA, the engine start temperature TMS is linked to a relative air charge rl via a map 11. By the relative air filling rl in the combustion chamber 4, the load dependence of the factor fLA is achieved. It is understood that instead of the relative air charge rl and a relative amount of fuel and / or an actual or desired lambda and / or an actual or desired torque or the like may be.

Also, the engine start temperature TMS is linked to an integrated air mass mli via a map 12. As a result, the value obtained from the map 11 is lowered with the internal combustion engine 1 warming up. The integrated air mass mli is a measure of the energy converted in the combustion chamber 4, which in turn has an increase in the temperature of the internal combustion engine 1 due to the associated burns. It is understood that instead of the integrated air mass mli also an integrated fuel mass and / or in the simplest case, the engine temperature TM can stand.

The output values of the two maps 11, 12 are multiplicatively linked, from which then the load-dependent factor fLA arises. The load-dependent factor fLA is additively linked to the basic factor fG, from which then the warm-up factor fWL arises.

Furthermore, a speed weighting fn of the warm-up enrichment of the internal combustion engine 1 is determined via a characteristic curve 13. Instead of the characteristic curve 13, a characteristic diagram can also be provided which, in addition to the speed dependence, is still dependent on a temperature or the relative air mass or the relative fuel mass.

This speed weighting fn can on the one hand, as in the FIG. 2 shown by a solid line, act directly on the load-dependent factor fLA via a multiplicative link. Alternatively, on the other hand, it is possible that the rotational speed weighting fn acts multiplicatively on the sum of the load-dependent factor fLA and the basic factor fG, as shown in FIG FIG. 2 is shown in dotted lines.

Additionally, it is possible in another branch of the FIG. 2 provide a characteristic or map dependent on lambda and which is multiplicatively or additively associated with one of the other branches described above.

The warm-up factor fWL is determined in a direct-injection internal combustion engine 1 in the manner described above as a function of the operating mode of the internal combustion engine 1. This means that the maps 10, 11, 12 and the characteristic 13 of the FIG. 2 are present for each of the operating modes of the internal combustion engine 1, ie in particular for the shift operation and the homogeneous operation.

If the internal combustion engine 1 is switched over between the different operating modes during warm-up, a change-over takes place with regard to the determination of the warm-up factor fWL. When the engine temperature TM approaches the operating temperature of the internal combustion engine 1, the warm-up factor fWL approaches unity and its influence on the fuel quantity to be injected approaches zero.

Is the basis of the FIG. 2 described warming factor fWL - deviating from the FIG. 1 - Used in internal combustion engines with intake manifold injection, the maps are 10, 11, 12 and the characteristic 13 of the FIG. 2 only once available, for the homogeneous operation. Switching between operating modes does not take place.

Claims (11)

1. Method for warming up an internal combustion engine (1), in which method fuel is injected into a combustion chamber (4), and in which method, below an operating temperature of the internal combustion engine (1), a warm-up factor (fWL) for increasing the injected fuel quantity is determined, characterized in that the warm-up factor (fWL) is determined from a base factor (fG) and from a load-dependent factor (fLA), with the load-dependent factor (fLA) being determined independently of the base factor (fG) for different operating modes.
2. Method according to Claim 1, characterized in that the load-dependent factor (fLA) is determined as a function of an integrated air mass (mli) and/or an integrated fuel mass and/or an engine temperature (TM) of the internal combustion engine (1).
3. Method according to one of Claims 1 or 2, characterized in that the load-dependent factor (fLA) is determined as a function of a relative air charge (rl) and/or a relative fuel quantity and/or an actual or nominal lambda value and/or an actual or nominal torque of the internal combustion engine (1).
4. Method according to one of Claims 2 or 3, characterized in that the load-dependent factor (fLA) is determined by multiplicative combination.
5. Method according to one of Claims 1 to 4, characterized in that the base factor (fG) is determined as a function of the engine temperature (TM).
6. Method according to one of Claims 1 to 5, characterized in that the load-dependent factor (fLA) and the base factor (fG) are combined with one another by addition.
7. Method according to one of Claims 1 to 6, characterized in that the load-dependent factor (fLA) or the sum of the load-dependent factor (fLA) and the base factor (fG) is weighted as a function of the rotational speed (n) of the internal combustion engine (1).
8. Method according to one of Claims 1 to 7, characterized in that the load-dependent factor (fLA) and/or the base factor (fG) and/or the warm-up factor (fWL) are determined as a function of an engine start temperature (TMS).
9. Control element, in particular read-only memory or flash memory, for a control unit (18) of an internal combustion engine (1), in particular of a motor vehicle, on which control element is stored a program which can be executed on a computer, in particular on a microprocessor, and which is suitable for carrying out a method according to one of Claims 1 to 8.
10. Internal combustion engine (1) in which fuel can be injected into a combustion chamber (4) during the warming-up, and having a control unit (18) for determining a warm-up factor (fWL) for increasing the injected fuel quantity below an operating temperature of the internal combustion engine (1), characterized in that the warm-up factor (fWL) can be determined by the control unit (18) from a base factor (fG) and a load-dependent factor (fLA), with it being possible for the load-dependent factor (fLA) to be determined independently of the base factor (fG) for different operating modes.
11. Control unit (18) for an internal combustion engine (1), in which internal combustion engine (1) fuel can be injected into a combustion chamber (4) during the warming-up, with the control unit (18) being provided for determining a warm-up factor (fWL) for increasing the injected fuel quantity below an operating temperature of the internal combustion engine (1), characterized in that the warm-up factor (fWL) can be determined by the control unit (18) from a base factor (fG) and a load-dependent factor (fLA), with it being possible for the load-dependent factor (fLA) to be determined independently of the base factor (fG) for different operating modes.

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