DE10222808B4 - Method for controlling the air / fuel ratio for an internal combustion engine - Google Patents

Abstract

Method for controlling the air / fuel ratio for an internal combustion engine, having the following structure:
An active cylinder crankcase ventilation, which communicates via a bypass with the outside air and is connected via separation elements a channel and a PCV valve connected to the intake tract,
A control system which, in accordance with an operating condition of the internal combustion engine, calculates an amount of fuel to be injected into the intake manifold or cylinder through fuel injection valves and calculates an amount of air supplied to the engine supplied to the engine through a throttle valve via the intake manifold,
A lambda probe connected to the control system,
characterized,
during the respective operating state of the engine via the detected exhaust gas values, the operating values of the supplied fuel, the combustion air and the engine oil temperature in the control unit, the composition of the total mass of the venting gas recirculated via the PCV valve is determined and in the control unit for adjusting the air supplied to the engine / Fuel ratio is taken into account.

Description

The The invention relates to a method for controlling the air / fuel ratio for one Internal combustion engine with the in the preamble of claim 1 mentioned features.

Previously known from the DE 100 36 128 A1 an internal combustion engine and a method for active ventilation of a cylinder crankcase (PCV = Positive Crankcase Ventilation). In this case, an intake tract of the engine for fresh air is connected via a bypass to the channel of the active ventilation of the cylinder crankcase. The cylinder crankcase is connected via an oil separator, a downstream PCV valve via a channel with the intake manifold of the engine. The suction pipe, the extracted from the cylinder crankcase, oil-laden air and blow-by gases and also recirculated exhaust gas are supplied to the intake.

previously known is it with PCV systems for the regulation of the motor supplied Air / fuel ratio, consider the fuel as a homogeneous medium, with a simple counter function each piston stroke for the entry is applied. With strong simplification of motor dependencies such as blow-by mass and engine temperatures will be an estimate of the fuel output from the lubricating oil determined and determined by one with the same inaccuracy Deducted entry and a resulting amount of memory. The fuel discharge amount leads to Reduction of injection quantity for the following combustion. The PCV gas mass flow is also compromised regarded as homogenous and its composition equated with air, although he next to the fuel vapors also contains blowby gases. Of the Influence of air mass change is applicatively compensated, that is, the increased air mass flow is in the engine control unit bill included additively. The engine oil temperature is either over the WIV function (maintenance interval extension) of the corresponding Sensor captured or highly abstracted modeled.

By The adoption of the fuel as a homogeneous medium can be considerable temperature dependencies the vaporisable fuel components are not accurately modeled and lead too big Inaccuracies in the injection mass calculation. The additive air correction contains no information about the composition of the PCV gas mass flow, which is a priority in Motors with a high blowby proportion lead to significant errors in the air mass calculation leads. The modeling of the oil temperature is high imprecise and guaranteed no reproducible results.

From the DE 198 14 667 A1 For example, an air-fuel ratio control system for an internal combustion engine is previously known in consideration of the venting of the fuel tank. In this case, the intake tract of the internal combustion engine is connected to the ventilation device of the fuel tank and comprises at least one fuel injection valve, which injects fuel into the internal combustion engine. The air-fuel ratio control system has an adsorption unit disposed between the fuel tank and the engine that adsorbs a fuel vapor emission gas generated in the fuel tank. Between the adsorption unit and the internal combustion engine, a suction system and a vent valve is arranged, which controls adjustable by the control unit, a flow rate of the adsorbed in the adsorption gas to vent the gas to the internal combustion engine.

The Control system consists of a first calculation device, the an amount of fuel to be injected in accordance with an operating condition the internal combustion engine calculated, further from a detection device, the one allowed Determined fuel quantity and a second calculation device, the an amount of to be vented from the adsorption Gas in accordance with the actual Calculated fuel injection quantity.

at this air / fuel ratio control system only the amount of fuel returned from the fuel tank vent is considered. An active ventilation of the cylinder crankcase and thus a consideration the oil-laden recirculated in this context Gases and the blowby gases is not provided.

From the US 5 331 940 A A method for controlling the air / fuel ratio of a crankcase ventilation internal combustion engine is known. In this case, the crankcase communicates with a first line, with which the crankcase outside air is supplied. Via a second line with a PCV valve arranged therein, the cylinder crankcase is connected to the intake passage of the engine. The sucked out of the cylinder crankcase and introduced into the intake duct blow-by gases are supplied to the engine together with the fuel-air mixture. To compensate for the influence of blowby gases In the lambda control, the influence of the venting gases is calculated as a function of the fuel quantity, the signal of the lambda sensor and the air quantity and taken into account in the adjustment of the fuel quantity.

adversely With this procedure is that with this regulation a qualitative and quantitative assessment of recycled PCV mass flow he follows. Thus, you can at high blow-by shares also significant errors in the air mass calculation occur.

Of the Invention is based on the object, a method of control the air / fuel ratio for one To provide an internal combustion engine with an actively ventilated cylinder crankcase with that in dependence from the oil-laden gases returned from the cylinder crankcase and the blowby gases actually needed in engine operation Fuel and air quantities can be adjusted and the recycled PCV mass flow can be assessed qualitatively and quantitatively.

These Task is achieved by the characterizing features of claim 1 solved.

Thereby, that while the respective operating condition of the engine over the detected exhaust gas values, the Operating values of the supplied Fuel, the combustion air and the engine oil temperature in the control unit occurring Composition of over the PCV valve returned total mass the vent gas is determined and in the control unit for adjusting the air / fuel ratio supplied to the engine considered becomes, both the recirculated fuel portion becomes as well as the combustion air content of the PCV total mass in the Control of the internal combustion engine supplied air / fuel ratio taken into account. Inaccuracies in the injection mass calculation of the fuel supplied to the engine and amount of combustion air are largely excluded. With the inventive solution are the the engine returned PCV total masses qualitatively and assessed and evaluated quantitatively.

Further advantageous embodiments are described in the subclaims, they are explained in the description together with their effects.

Based a drawing is an embodiment of the invention below described. In the corresponding Drawings show:

1 : a schematic representation of a PCV engine,

2 : a representation of the boiling characteristics of petrol fuels,

The embodiment further includes the following tables:
Table 1: a list of the masses occurring on the PCV engine,
Table 2: a list of existing dependencies,
Table 3: a list of the fuel mass flow calculation,
Table 4: a list of the air mass flow calculation,
Table 5: a model principle of the PCV adaptation via lambda,
Table 6: a list of additional functions.

content The invention is a method that runs in the engine control unit and at any time the current composition of the sucked charge and their air and fuel components determined and accordingly one adjusted injection quantity calculated.

• – das Siede- und Kondensationsverhalten des Kraftstoffes wird in mindestens 2, besser mehr Temperaturbereiche aufgeteilt, um den weiten Siedebereich der Kraftstoffkomponenten hinreichend genau darzustellen (siehe 2),
• – der Erwärmungs-, Brenn- und Alterungsvorgang eines Verbrennungsmotors,
• – den Anteil an Inertgas des Blowby-Gases,
• – Verwendung des Öltemperatursignals aus der Ermittlung des Ölwechselintervalls,
• – weitere motoreigene Funktionen, wie beispielsweise Motorverschleiß zur Modellpräzisierung.

The following parameters are considered in the approach:

• - The boiling and condensation behavior of the fuel is divided into at least 2, better more temperature ranges in order to represent the wide boiling range of the fuel components with sufficient accuracy (see 2 )
• The heating, burning and aging process of an internal combustion engine,
• The proportion of inert gas of the blow-by gas,
• Use of the oil temperature signal from the determination of the oil change interval,
• - Other engine-specific functions, such as engine wear for model precision.

Fuel path - according to the table 3

• - In the warm-up phase of an internal combustion engine increases its thermal Implementation rate many times faster than the engine oil temperature.
• - The Engine oil temperature is decisive for evaporation of the registered fuel.
• - Below a threshold value of the heat supplied to the combustion chamber can be due to the leakage of pure fuel and its complete entry into the oil. This is weighted with a warm-up factor F_WL.
• - With increasing temperature improves the mixture preparation, whereby the low-boiling components remain predominantly in the combustion chamber and only the heavier in the oil reach. Therefore, F_WL must be for the n temperature ranges are stored.
• - Becomes no heat supplied this means, the starter turns the engine without incipient combustion (starting problems), the fuel input is weighted with a start factor (F_ST) possibly also in dependence from the starting temperature.
• - Above the heat threshold value is the fuel input only of the set fuel-air mixture dependent, because more fuel mass is available in the intake and compression tract. This is compensated with a mixture factor F_G. From o. G. Reasons he also filed n-fold.
• - All just mentioned effects are inseparable from the engine start temperature coupled and are accordingly represented in function of this.
• - As soon as while the warming of the engine oil begin to reach the boiling point of the first fuel to drown them out.
• - A fuel vapor mist forms, which is torn in the direction of the intake manifold by the system's own aeration mass flow (mPCV). ( 1 )
• - Of the Fuel content of this mass flow is of its relative saturation dependent and can be the absolute saturation (mKS_PCV_max). The saturation factor F_S consists of: - Share of non-condensed KS from Blowby F_BB, - Evaporation potential from accumulated fuel masses in n classes F_m_n (the more mass was registered, the more can evaporate), - Distillation the n fuels at T_Öl (the bigger T_Öl, the more stronger lightly boiling off vapors while high-boiling ones still remain in the oil and only at higher Evaporate temperature ranges) - maximum fuel / air ratio (saturation ratio) in PCV gas depending from intake manifold temperature F_FA (intake manifold is the coldest part on the way of the Fuel to the combustion chamber, and this is why there already condense in part).

Air path - according to the table 4

• - The over the PCV system fed to the intake manifold venting mass will over a throttle of a pneumatic valve controlled intake manifold pressure dependent and the fresh air supply is limited. As a result, this total gas mass defined throughout the operating range (speed, load, temperature), reproducible and thus for to consider each individual operating point as constant.
• - These Gas mass is stored in a corresponding model.
• - The PCV gas mass is composed of air (ventilation or ventilation air), Blowby and fuel mass.
• - During the Duration initially decreases the blowby mass (inlet effect). In case of increased wear (increased mileage) she goes over the new condition.
• - The Composition of the blowby from fresh air and from the combustion originating inert gases is dependent from operating point and wear pattern.
• - If if the PCV mass remains the same (see above) the blowby percentage increases, will sink according to the proportion of ventilation, so is the off Inertgasanteil originating from the Blowby at the PCV mass flow depends on Mileage and operating condition. This relationship is with the Blowby factor over Mileage (F_LL) shown and the fresh air proportion accordingly elevated or reduced.

Model matching by means of lambda regulation - accordingly Table 5

• - By the more precise Modeling the effects of a PCV system on fuel and air path is it is possible occurring mixture deviations in the exhaust gas (which by the lambda probe captured and the control unit supplied as value) better the individual elements of the engine periphery and thus also assigned to the PCV system.
• - So long the injection mass calculated from the intake air mass measured lambda in the exhaust gas is neither a fuel input still -austrag determine. The calculated and supplied fuel masses stay unchanged.
• - Below the IST_Lambda the setpoint significantly, it is assumed that the mixture enrichment in the exhaust gas from evaporated fuels from the oil comes. It is checked whether the engine oil above the temperature limiting the lowest temperature range T1 is located. If this is not the case, it can be assumed that no KS evaporation process has yet begun. Thus, can a KS river over the PCV are excluded and the error must be another System can be assigned. The calculated n fuel masses remain unchanged.
• - Lies the oil temperature however, above the first threshold, it is checked if they even the second one exceeds. If this is not the case, then the lambda offset is used and the calculated fresh air mass a fuel mass difference determined. This amount corresponds to the PCV-KS mass flow and will written in a memory. At the same time the injection mass the subsequent combustion and the accumulated mass of the lowest Temperature range reduced by their amount. In the next calculation cycle the memory is updated. The same applies to all n subsequent ones Temperature ranges.
• - doing so but is dependent the oil temperature and the saturation criteria mentioned under Fuel Path a weighting of the mass shares made. These in turn serve the memory update and are selectively from the corresponding Deducted temperature ranges.
• - Results the desired-actual lambda comparison is too lean a mixture in the exhaust gas, so the injected fuel was not optimally enforced. It it is assumed that the missing mixture leading to Fuel mass over the annular gap between the piston and cylinder wall enters the crankcase is. It is checked whether the temperature of the engine oil above the temperature limiting the lowest temperature range T1 is located. If this is not the case, it can be assumed that still no fuel evaporation process has used. Thus, fuel flow through the PCV can be ruled out and the total fuel error rate will be on the n temperature ranges equally distributed. There is an increase the corresponding storage values, accumulated masses and the injection time.
• - Lies the oil temperature however, above the first threshold, it is checked if they even the second one exceeds. If this is not the case, then the fuel error mass becomes the remaining n-1 temperature ranges according to the oil temperature and as an inversion of the evaporation path mentioned under the item "fuel path" weighted and distributed. The same applies to all n subsequent ones Temperature ranges.
• - Lies the engine oil temperature however over the highest Temperature range limiting threshold, so the error has a be assigned to another system.

Next functions - according to the table 6

• - Of the Fuel input and discharge is vapor pressure dependent. The lower the vapor pressure, the less fuel remains gaseous in the combustion chamber. Thereby testifies an elevated Fuel input of lower vapor pressure and vice versa. About the function described in the model matching by means of lambda control this deviation is determined and as a vapor pressure change z. B. the start injection amount correction provided.
• - Farther The fuel input is significantly dependent on the blowby and thus the engine wear. Thus, over runtime the averaged fuel input is compared to a reference value. Leave it get a statement about increased or reduced engine wear.
• - Under certain boundary conditions such as wear state, temperature, and speed Is it possible, that at full load in the crankcase by increased blowby an overpressure builds up, which propagates to the intake manifold. This will be the measured Intake manifold pressure greater than the ambient pressure and leads to falsification the ambient pressure calculation. This must be dependent from the above wear a corresponding reduction respectively.

Table 1

masses

• m _air ^exhaust

  stoichiometric air mass in exhaust

  m _air ^suction

  entire sucked air mass

  ^m air ^PCV

  sucked in via the PCV system air mass

  m _air ^ventilation

  PCV Spülfrischluft

  m _KS ^Inj

  injected fuel mass

  M _KS ^exhaust

  stoichiometric fuel mass in the exhaust

  m _KS ^bypass

  by Wandanlagerung outflowing Fuel mass

  m _KS ^oil

  Fuel mass in the oil

  m _KS ^PCV

  Fuel mass out the oil

  M _blowby

  Blowby mass (inert gas, HC, water and fresh air)

  m _PCV

  PCV total mass

Table 2

dependencies

• m air exhaust  = m air Suction  - f air (m blowby )
• m air Suction  = f (p atm ; p Suction ; n; t air ; m air PCV )
• m air PCV  = m air ventilation  + f air (m blowby )
• m air ventilation  = f (p atm ; p KK ; p Suction ; n; t air )
• m KS inj  = m air Suction / λ / A / F - ratio - m KS PCV
• m KS exhaust  - m KS inj  + m KS PCV  - m KS bypass  - f KS (m blowby )
• m KS bypass  = f (p Suction ; n; t mot ; t oil ; km - LL)
• m KS oil  = m KS oil  + m KS bypass  + f KS (m blowby ) - m KS PCV
• m KS PCV  = f (m PCV ; m KS oil ; t oil ; t air )
• m blowby  = f (p Suction ; p KK ; n; t mot ; t oil ; km - LL)
• m PCV  = (m air ventilation  + m blowby  + m KS PCV )

Table 6

More functions

Fuel detection

• since m _KS ^bypass and m _KS ^PCV depending on the KS-vapor pressure

Blow / wear recognition

• because m _KS ^oil and m _KS ^PCV depending on the _blowby m

Correction of atmospheric pressure

Since p _suction near full load depends on m _blowby (old engine)

Claims (10)

A method for controlling the air / fuel ratio for an internal combustion engine, comprising: - an active cylinder crankcase ventilation, which communicates via a bypass with the outside air and connected via separation elements a channel and a PCV valve connected to the intake manifold, A control system which, in accordance with an operating condition of the internal combustion engine, calculates an amount of fuel to be injected into the intake manifold or cylinder through fuel injectors and calculates an amount of air supplied to the engine through a throttle valve supplied to the engine via the intake manifold; Lambda probe connected control system, characterized in that during the respective operating state of the engine via the detected exhaust gas values, the operating values of the supplied fuel, the combustion air and the engine oil temperature in the control unit, the occurring Zusamme Determination of the recirculated via the PCV valve total mass of the vent gas is determined and is taken into account in the control unit for adjusting the air / fuel ratio supplied to the engine. Method according to claim 1, characterized in that that the returned fraction shares of the fuel in the vent gas from the temperature of the oil and dependent from the previously determined entry of fractions of the fuel in the oil be determined. Method according to one or more of the previous ones Claims, characterized in that the recycled fractional fractions of Fuel and the proportion of inert gas in the blowby gas depending of warming, Burning and aging process of the engine can be determined. Method according to one or more of the previous ones Claims, characterized in that for several Temperature ranges of the oil or fuel, respectively, a warm-up factor for the boiling and distillation behavior of the fuel stored in the memory of the control unit and readable is. Method according to one or more of the previous ones Claims, characterized in that when starting the engine a stored Start factor considered and read out. Method according to one or more of the previous ones Claims, characterized in that above a threshold value of the engine temperature the fuel input with a to the respective engine temperature or Correction factor stored for the respective engine temperature range becomes. Method according to one or more of the preceding claims, characterized in that the fuel content, in which the motor is determined by the total mass of venting gas returned by the PCV valve taking into account a saturation factor which depends on - the proportion of non-condensed fuel from Blowby, - the registered in the oil fuel masses and their boiling and evaporation behavior in fixed law th temperature ranges, - the respective oil and intake pipe temperature is formed. Method according to one or more of the previous ones Claims, thereby in that - one Value in the memory of the control unit is filed for each operating point is constant and the air mass recirculated via the PCV valve characterized, - one Value for the recirculated air mass dependent on from the term, the wear pattern and corrected by the respective operating point of the engine in the control unit becomes, and by means of the values determined in the control unit, the setting the supplied to the engine Air masses takes place. Method according to one or more of the previous ones Claims, characterized in that over the Lambda control over the PCV valve depending from the engine oil temperature returned fuel mass according to their boiling and evaporation behavior in the respective Temperature range determined and in the motor to be supplied total fuel quantity considered becomes. Method according to one or more of the previous ones Claims, characterized in that the adjustment of the air / fuel ratio supplied to the engine dependent on the vapor pressure of the fuel, the engine wear and the corrected atmospheric pressure he follows.