DE10101006A1 - Controlling quantity of fuel delivered during starting of internal combustion engine comprises increasing quantity of fuel delivered by starting quantity increasing factor - Google Patents

Abstract

Controlling the quantity of fuel delivered during a starting process of an internal combustion engine, in which the quantity of fuel delivered is increased by a starting quantity increasing factor (F), comprises initially setting the factor (F) to a starting factor (F1) after reaching a first threshold value (Sn1) for an engine revolution (n) to a first time point (t1), determining a second time point (t2) after reaching the threshold value, raising the starting factor when the engine revolution lies below the a second threshold value (Sn2) and/or the revolution is changed after raising to the first time point below a threshold value, and canceling the starting quantity increasing factor after successfully starting the engine.

Description

The invention relates to a method for controlling an amount of fuel supplied during a starting process of an internal combustion engine with the in the preamble of claim 1 mentioned features. It also concerns uses of the Method according to claims 12 and 13.

A cold start or a start process at low engine temperatures requires under other special control measures in the field of fuel supply. The starting process can be divided into individual phases. First, the engine accelerated to a minimum speed by the starter. After reaching the A minimum amount of fuel is provided which is compared to Amounts of fuel are significantly increased under higher operating temperatures. This Raising is usually done with or shortly after the startup Internal combustion engine withdrawn to a target idle speed.

A basic problem in the startup process with both spark ignited, in particular direct injection, internal combustion engines (gasoline engines) as well self-igniting engines (diesel) is the wetting of the combustion chamber walls, the valves, the piston crown and the intake manifold with a fuel film. This one, also as Known disadvantage of wall film problems can be seen, for example, in one Direct injection, in the tendency of the injected fuel to adhere to the To deposit the piston crown on which the injection jet is usually directed. As a result, substantial portions of the inducted or injected Amount of fuel not burned the first time the engine was started because of of the engine, which is still cold in the area, cannot evaporate. Thus in Generally too much fuel is provided, which results in the exhaust gas during the start process significantly increased proportions of not or incompletely burned Contains hydrocarbons. Because even the incomplete conversion burned hydrocarbons in the exhaust system arranged catalyst systems in have not yet reached their minimum operating temperature, one rises  Total emission of the motor vehicle, so compliance with the law Pollutant limits is difficult.

The problem is exacerbated by the fact that in conventional solutions the Raising the fuel supply to the fuel during the starting process particularly poor starting properties, i.e. with low vapor pressure Otto engines and / or low ignitability in diesel fuels, is coordinated. Known solutions only provide a starting quantity increase factor in Influencing dependence on the engine temperature. The starting quantity The increase factor is reduced with increasing engine temperature. The factor and orient the characteristic of the withdrawal of the starting quantity increase factor depend essentially on the fuel properties and are therefore low Fuel qualities designed. Usually, however, are for those in circulation Motor vehicles have better fuel qualities available.

The object of the present invention is therefore to provide a method for adapting a amount of fuel supplied during a starting process To provide internal combustion engine, through which a better adaptation of the starting quantity increase factor to the actual conditions during the Starting process can take place. In connection with this, the total emission of the Motor vehicle be reduced.

This object is achieved by a method with the features of claim 1. According to the invention it is provided that

• a) after reaching a first threshold value for an engine speed Starting quantity increase factor initially to an initial starting quantity Raising factor is set
• b) predetermined a second point in time or by reaching a threshold value determined for a number of revolutions since the start of the starting process becomes,
• c) the starting quantity increase factor is increased when the engine speed at the second point in time below a second threshold value and / or a Change in engine speed since the start of the increase below one Threshold is and  
• d) the starting quantity increase factor after successful engine start, that is after the start of the ramp-up.

This usually results in lower fuel quantities during the starting process fed. As a result, wall film formation is reduced and the total emission is reduced unburned hydrocarbons HC and carbon monoxide CO of the motor vehicle is lowered.

According to a preferred embodiment of the method, the Starting quantity increase factor depending on an elapsed time from the start the starting process, the number of engine revolutions since the start of the starting process, the engine speed and / or the engine speed change. In this way, the amount of fuel supplied is particularly accurate during actual needs of the starting process are adjusted and the wall film formation is largely pushed back.

It is further preferred that the starting quantity increase factor by specifying a maximum starting quantity increase factor is limited. The maximum starting quantity Raising factor can, in particular, depend on parameters such as the Engine temperature, the number of engine revolutions and the elapsed time since Start of the starting process, the amount of fuel already supplied and / or Engine speed. By limiting the start quantity Oversteer is avoided.

In a further preferred embodiment of the method, a third point in time predetermined or by reaching a threshold for the number of Revolutions determined since the start of the starting process. The starting quantity The boost factor is reduced when the engine speed reaches the third point in time below the second threshold for engine speed and / or Threshold for the engine speed change is. In this way, one oversized wall film formation with poor fuels can be avoided.

In a further preferred embodiment, the last-mentioned procedure is when reaching a fourth point in time, the start process is aborted, if the Engine speed below the second threshold or the threshold for the Engine speed change is. The fourth point in time can be predefined.  

It is also conceivable to use the fourth point in time on the basis of a threshold value for the number To determine revolutions since the start of the starting process. A starter company from Engine control unit is preferably at the same time or delayed when the Start process prevented.

In the event of the starting process being aborted, it is preferred to use one subsequent and if necessary in further repetition starts immediately with the maximum starting quantity increase factor to start the fuel supply. A fifth point in time is preferably specified for the repeat starts or by Reaching a threshold for the number of revolutions since the beginning of the Starting process determined. The starting quantity increase factor is reduced when the Engine speed at the fifth point in time below the second threshold value and / or the threshold value for the engine speed change. Also an ongoing one Repeat start can be canceled and by one or more subsequent ones Repeat starts are replaced. A successful start can be achieved by reaching a Idle speed or based on a change in speed in a predetermined Time interval (start-up detection) can be determined.

The method is preferably used when the Internal combustion engine a gasoline engine, especially a direct injection Petrol engine, is. The use of the method is also preferred for self-igniting Internal combustion engines (diesel).

Further advantageous embodiments are the subject of the remaining subclaims.

The invention is described below in exemplary embodiments on the basis of the associated Drawings explained in more detail. Show it:

FIG. 1 is a curve of a starting quantity increase factor, an engine speed and a lambda value against a pre-catalytic converter during a starting process in the prior art;

Fig. 2 is a curve of the starting quantity increase factor, the engine speed and the lambda value before the primary catalytic converter during a starting process according to the inventive method;

Fig. 3 is as Figure 2 but with a poor fuel and linear increase in the starting quantity increase factor.

Fig. 4 is as Figure 3 but with stepped increase in the Startmengen- increase factor.

Fig. 5 shows a course of the starting amount increase factor and the engine speed with an extremely poor fuel and

Fig. 6 shows a curve of the starting quantity increase factor and the engine speed at a repeat start with an extremely poor fuel.

Fig. 1 shows the time course of a starting quantity increase factor F, an engine speed n and a lambda value λ in front of a primary catalytic converter during a starting process in conventional process control. The courses shown are of course only to be seen schematically and can take slightly different courses in a specific embodiment for a specific internal combustion engine. The necessary means for carrying out the increase in internal combustion engines are known. In particular, controllable injection systems for self-igniting or spark-ignited engines are known, with which the fuel supply can be controlled at least quantitatively. Coordination of individual units involved in the starting process can take place in a known manner via an engine control unit.

With the start of the starting process (time t ₀ ), the internal combustion engine is initially subjected to a torque by means of a starter until a first threshold value S _n1 for the rotational speed n is reached (time t ₁ ). From time t ₁ , the fuel supply is started by injection or intake. The quantity of fuel supplied is increased during the starting process by a starting quantity increase factor F _kon and is kept at a constant value for a predeterminable interval, for example until the engine speed n has reached a desired idling speed n _empty (time t ₂ ). After reaching time t ₂ , the conventional starting quantity increase factor F _{kon is} gradually reduced to the value 1 and the increase in the fuel supply is thus reduced. A dimensioning of the conventional starting quantity increase factor F _kon is specified in such a way that a successful starting process is still possible even with extremely poorly vaporizable and / or flammable fuels. However, this also means that strong wall film formation has to be accepted. During the first ignitions, a substantial part of the fuel cannot burn and thus considerably increase the emission of incompletely burned hydrocarbons. The high injection quantity leads to a very rich exhaust gas, whereby the area integrals below a λ = 1 line provide an indication of the HC emissions during the starting process (area 10 ). The larger the area 10 , the higher the HC emission. At this early stage, the catalyst systems for converting incompletely burned hydrocarbons were not yet heated to operating temperature.

In FIG. 2, the curves of the starting quantity increase factor F, the engine speed n and the lambda value λ in front of the primary catalytic converter according to -the method of the invention using a commercial fuel guide shown. After starting (time t ₀ ), the engine is first accelerated by the starter until the first threshold value S _{n1 is} reached (time t ₁ ). When the threshold value S _n1 is reached, the fuel supply is released in such a way that initially a low starting quantity increase factor F _{1 is} specified (for comparison purposes, the conventional starting quantity increase factor F _{kon is also} entered). At the start of the start, a second time t _{2 is} specified at the same time or determined by reaching a threshold value for a number of revolutions since the start of the start process.

In the present case, the fuel quality is so good that a successful start was recognized before the second time t ₂ was reached. The successful start can be recognized in a manner known per se by reaching the desired idling speed n _empty or by means of a run-up detection. During the run-up detection, a change in speed is tracked in a predetermined time interval. If the speed change exceeds a predefinable threshold value for the motor speed change, a successful start is assumed. After the engine starts, the starting quantity increase factor F is gradually reduced to the value 1. It becomes clear that, compared to conventional start-up control, significantly lower amounts of fuel are injected and consequently the emission of unconverted hydrocarbons is also reduced (area 10 ).

FIG. 3 shows a starting process according to the method according to the invention analogous to FIG. 2 but with a fuel of poor quality. At time t ₂ , which - as already described above - is determined, the starting process has not yet been successfully completed. The starting quantity increase factor F is increased when the engine speed n at time t _{2 is} below a second threshold value S _n2 and / or a change in engine speed since the start of the increase (time t ₁ ) is below a threshold value. An increase in the starting quantity increase factor F is largely linear here. The increase in the starting quantity increase factor F can be carried out as a function of an elapsed time since the start of the starting process, the engine speed n and / or the change in engine speed, so that courses other than linear are also conceivable.

If the start-up detection signals a successful start, the Starting quantity increase factor F is gradually reduced back to the value 1. in the Generally, the total emission of hydrocarbons during a starting process with the present fuel quality still significantly lower than at the state of the Technology. Due to the possibly longer start time, the emissions may increase Hydrocarbons will rise through the internal combustion engine, however the peak emissions have been postponed. subordinate Catalyst systems can then already reach their minimum operating temperature Conversion of pollutants have reached, so that a total emission of Motor vehicle sinks.

FIG. 4 shows an alternative increase in the starting quantity increase factor F with otherwise the same boundary conditions as in the starting process according to FIG. 3. Instead of a linear increase, the starting quantity increase factor F is gradually increased until the engine start-up detection detects a successful start.

In FIG. 5, a startup process is n with an extremely poor and non-standard course of the fuel at the engine speed and the starting quantity increase factor F shown. As already explained above, the starting quantity factor F is increased if the second threshold value S _n2 and / or the threshold value for the engine speed change is not exceeded at the time t ₂ . The increase is initially linear, but is limited overall by specifying a maximum starting quantity increase factor F _max . The maximum starting quantity increase factor F _max is intended to prevent excessive wall film formation and can be determined as a function of an engine temperature, a number of engine revolutions since the start of the start process, a time interval since the start of the start process, an amount of fuel already supplied and / or the engine speed n.

Simultaneously with the start of the increase, a third point in time t _{3 is} specified or determined by reaching a threshold value for the number of revolutions since the start of the starting process. The starting quantity increase factor F is reduced if the engine speed n at time t ₃ is still below the second threshold value S _n2 and / or the threshold value for the engine speed change in order to prevent excessive film film wetting. The lowering takes place, for example, linearly up to a level which can deviate from the initial start quantity increase factor F ₁ , preferably exceeding the initial start quantity increase factor F ₁ .

If a successful starting process could not yet be carried out by the time t ₃ , a fourth time t _{4 is} predetermined or determined by reaching a threshold value for the number of revolutions since the start of the starting process. The starting process is terminated when the engine speed n is below the second threshold value S _n2 or the threshold value for the engine speed change at the time t ₄ . At the same time or with a time delay when the starting process is interrupted, starter operation is prevented by the engine control unit, so that a new attempt to start is only possible with a time delay due to the starter being re-engaged.

If, as in the present case, the starting process is interrupted, at least one subsequent repeat start can be initiated in accordance with the procedure shown in FIG. 6. When starting again, the _maximum starting quantity increase factor F _{max is} started immediately after reaching the first threshold value S _{n1 in} order to protect a battery in the motor vehicle. At the same time, a fifth point in time t _{5 is} specified or determined by reaching a threshold value for the number of revolutions since the start of the starting process. If the engine speed n at time t _{5 is} still below the second threshold value S _n2 and / or the threshold value for the engine speed change, the starting quantity increase factor F is reduced. Of course, an ongoing repeat start can also be canceled and repeated by one or more subsequent repeat starts.

LIST OF REFERENCE NUMBERS

10

Area for estimating HC emissions during the starting process
F Starting quantity increase factor
F ₁

Initial starting quantity increase factor
F _con

conventional starting quantity increase factor
F _max

maximum starting quantity increase factor
n speed
n _empty

Idle speed
S _n1

; first threshold for engine speed n
S _n2

second threshold value for engine speed n
t ₀

Start of the start process
t ₁

Start of raising and first time
t _2-5

further times

Claims (13)

1. Method for controlling an amount of fuel supplied during a starting process of an internal combustion engine, in which the amount of fuel supplied is increased by one. Starting quantity increase factor is increased, characterized in that

• a) after reaching a first threshold value (S _n1 ) for an engine speed (n), the starting quantity increasing factor (F) is initially set to an initial starting quantity increasing factor (F ₁ ) (time (t ₁ )),
• b) a second point in time (t ₂ ) is predetermined or is determined by reaching a threshold value for a number of revolutions since the start of the starting process,
• c) the starting quantity increase factor (F) is increased if the engine speed (n) at time (t ₂ ) is below a second threshold value (S _n2 ) and / or an engine speed change since the start of the increase (time (t ₁ )) is below one Threshold is and
• d) the starting quantity increase factor (F) is withdrawn after a successful engine start.

2. The method according to claim 1, characterized in that the raising of Starting quantity increase factor (F) depending on an elapsed time since Start of the starting process, the number of engine revolutions since the start of the Starting process, the engine speed (s) and / or the engine speed change takes place. 3. The method according to claims 1 or 2, characterized in that the starting quantity increase factor (F) is limited by specifying a maximum starting quantity increase factor (F _max ). 4. The method according to claim 3, characterized in that the maximum starting quantity increase factor (F _max ) as a function of an engine temperature, a number of engine revolutions since the start of the starting process, a time interval since the start of the starting process, an amount of fuel already supplied and / or Engine speed (s) is determined. 5. The method according to any one of claims 1 to 4, characterized in that

• a) a third point in time (t ₃ ) is predetermined or is determined by reaching a threshold value for the number of revolutions since the start of the starting process and
• b) the starting quantity increase factor (F) is reduced if the engine speed (n) at time (t ₃ ) is below the second threshold value (S _n2 ) and / or the threshold value for the engine speed change.

6. The method according to claim 5, characterized in that

• a) a fourth point in time (t ₄ ) is predetermined or determined by reaching a threshold value for the number of revolutions since the start of the starting process and
• b) the starting process is interrupted when the engine speed (n) at time (t ₄ ) is below the second threshold value (S _n2 ) or the threshold value for the engine speed change.

7. The method according to claim 6, characterized in that at the same time or Delayed from starting the starter operation from Engine control unit is prevented. 8. The method according to claims 6 or 7, characterized in that after termination of the starting process with at least one subsequent repeat start, the maximum starting quantity increase factor (F _max ) is started immediately. 9. The method according to claim 8, characterized in that

• a) a fifth point in time (t ₅ ) is predetermined or determined by reaching a threshold value for the number of revolutions since the start of the starting process and
• b) the starting quantity increase factor (F) is reduced if the engine speed (n) at time (t ₅ ) is below the second threshold value (S _n2 ) and / or the threshold value for the engine speed change.

10. The method according to claims 8 or 9, characterized in that a ongoing repeat start can be canceled and by one or more subsequent repeat starts is repeatable. 11. The method according to any one of claims 1 to 10, characterized in that a successful start is determined by reaching an idle speed (n _empty ) or based on a speed change in a predetermined time interval (run-up detection). 12. Using a method of controlling an amount of fuel supplied during a starting process of an internal combustion engine according to one of the Claims 1 to 11, characterized in that the Internal combustion engine a gasoline engine, especially a direct injection Petrol engine, is. 13. Using a method of controlling an amount of fuel supplied during a starting process of an internal combustion engine according to one of the Claims 1 to 11, characterized in that the Internal combustion engine is a diesel engine.