DE10115969B4 - Method for determining a quantity of fuel supplied during a starting process of an internal combustion engine - Google Patents

Abstract

Method for determining a quantity of fuel supplied during a starting process of an internal combustion engine, in which the supplied fuel quantity is changed by a starting quantity factor (F _i ), characterized in that
(A) the starting operation of the internal combustion engine is divided into two start phases with an arbitrary number of individual injection events (i) and for each injection process (i) a start quantity factor (F _i ) is determined,
(b) decreasing or maintaining the starting amount factor (F _i ) in each new injection operation (i) of the first starting phase until a successful startup of the internal combustion engine is indicated by a run-up detection (HE), wherein a magnitude of the starting quantity factor (F _i ) during the first start phase in dependence on an engine temperature (T _M ), a height of a predetermined start quantity factor (F _i-1 ), a cylinder number (Z) and / or a historical history (τ) of previous starting operations and the duration of a monitoring interval (dt ₁ ) of the first starting phase is determined by the engine temperature (T _M ), the number of cylinders (z) and / or a time threshold (y) dependent on a starter setpoint speed,
(c) the starting quantity factor (F _i ) in each new ...

Description

The The invention relates to a method for determining a quantity of fuel supplied during one Starting process of an internal combustion engine with the in the preamble of claim 1 features. It also relates to uses the method according to the claims 17 and 18.

One Cold start or a startup at low engine temperatures requires, inter alia, special control measures in the area of fuel supply. The boot process can be here break down into individual phases. First the starter is accelerated to a minimum speed. After this Reaching the minimum speed, an amount of fuel is provided, compared to fuel quantities under operating temperatures is clearly raised. This increase usually ends with or shortly after the start of the run-up of the internal combustion engine a target idling speed.

One Basic problem during the starting process both in spark-ignited, in particular direct-injection internal combustion engines (gasoline engines) as well as self-igniting Engines (Diesel) is the wetting of the combustion chamber walls, the valves, the piston crown and the suction tube with a fuel film. This, also known as wall film problem drawback shows up, for example in a direct injection, in the tendency of the injected fuel, on the piston crown, to which the injection jet usually is aimed to cut off. As a result, substantial portions become the amount of fuel sucked or injected at the first ignitions the engine was not burned because of it in the environment yet cold engine can not evaporate. Thus, generally too much fuel is provided, which is As a result, an exhaust gas during significantly increased the starting process Shares in not or incomplete contains burnt hydrocarbons. As well as the conversion the incomplete burned hydrocarbons in the exhaust system arranged catalyst systems usually not yet reached their minimum operating temperature have a total emission of the motor vehicle increases, so that the Compliance with legal pollutant limits is difficult.

The Problem is compounded by the fact that in the conventional solutions increasing the fuel supply during the starting process Fuels with particularly poor starting properties, that is with low Vapor pressure in gasoline engines and / or low ignition in diesel fuels, is agreed. Known solutions So far only provide a starting quantity factor depending on influenced by the engine temperature or engine speed. Of the Starting quantity factor, for example, with increasing engine temperature reduced. The factor and the characteristic of the subsequent withdrawal The starting quantity factor is essentially based on the fuel properties and are therefore designed for low fuel qualities. Usually are however for In-vehicle motor vehicles have better fuel qualities available.

DE 30 42 245 A1 describes an electronic engine control system with signal generators for fuel metering and ignition during takeoff. The starting phase is divided into at least three phases. In a first phase, a temperature-dependent constant excess amount is metered, wherein a duration of this phase depends on the speed or a maximum value with respect to the number of revolutions of an engine shaft. In a subsequent second phase, a change in quantity follows, depending on at least one of the variables engine temperature, speed and total number of revolutions, until a limit value has been reached. In a subsequent third phase of this temperature-dependent limit is maintained and the ignition during the start depending on at least speed or temperature adjusted to early.

One Another problem is the occurrence of undesirable speed overshoots over the given Idle speed. Such overrides occur during startup by default to high starting amount factors up and lead to an unnecessary Increase in fuel consumption and increase in total emissions Internal combustion engine.

task The present invention is therefore a method of detection a supplied needs-based Fuel quantity during a starting process of an internal combustion engine available to overcome the mentioned disadvantages of the prior art can be. In particular, it should be improved by a regulated adaptation of the Starting quantity factor to the actual conditions a fast and smooth startup process be ensured. This should be accompanied by the total emissions of the motor vehicle and reduces the occurrence of speed overshoots be avoided.

• (a) der Startvorgang der Verbrennungskraftmaschine in zwei Startphasen mit einer beliebigen Anzahl einzelner Einspritzvorgänge gegliedert ist und für jeden Einspritzvorgang ein Startmengenfaktor bestimmt wird,
• (b) der Startmengenfaktor in jedem neuen Einspritzvorgang der ersten Startphase vermindert oder beibehalten wird, bis ein erfolgreiches Hochlaufen der Verbrennungskraftmaschine durch eine Hochlauferkennung angezeigt wird,
• (c) der Startmengenfaktor in jedem neuen Einspritzvorgang der sich anschließenden, zweiten Startphase verändert oder beibehalten wird, bis ein erfolgreiches Erreichen einer Leerlaufdrehzahl beispielsweise durch eine Leerlauferkennung angezeigt wird (erfolgreicher Motorstart), und
• (d) der Startmengenfaktor nach erfolgreichem Motorstart zurückgenommen wird oder andere Motorsteuerungsfunktionen die Anforderung einer Gemischanreicherung übernehmen.

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

• (a) the starting process of the internal combustion engine is divided into two starting phases with an arbitrary number of individual injection processes and a starting quantity factor is determined for each injection process,
• (b) reducing or maintaining the starting amount factor in each new injection operation of the first starting phase until a successful startup of the internal combustion engine is indicated by a run-up detection,
• (c) changing or maintaining the starting amount factor in each new injection operation of the subsequent second start phase until a successful achievement of an idling speed is indicated, for example, by an idle detection (successful engine start), and
• (d) the starting quantity factor is withdrawn after successful engine start, or other engine control functions accept the request for mixture enrichment.

In order to are usually during the startup process supplied smaller amounts of fuel. in the As a result, the wall film formation is reduced and the total emission of the motor vehicle is lowered. By the implementation of the invention Startup can be overrides, to speed overshoots to lead, effectively prevent.

According to the procedure a determination of the height is made a starting quantity factor during the first starting phase depending on from the engine temperature, a height a predetermined starting quantity factor, a number of cylinders and / or a historical history of previous starts. The latter has the advantage, for example, with increasing operating time the internal combustion engine drifting occurring the starting quantity factor at the beginning of the boot process early to compensate. So can for example, age-related gradual increases in the starting quantity factor taken into account so that the boot process does not unnecessarily lengthen. On the other hand you can by considering the historical course of previous take-offs also suppression phenomena are pushed back, by optionally lowering the amount of fuel provided Specification of lower starting quantity factors. The consideration previous start cycles when setting the current start quantity factor has the advantage that a start of the acceleration of the internal combustion engine much more uniformly feasible and known sources of error early can be counteracted.

It has also proved to be advantageous when the starting quantity factor while the first starting phase at engine temperatures in the range of 15 to 30 ° C around 10 to 70%, in particular 20 to 50%, is reduced. This is the Reduction of the value exceeding 1 Share of the starting quantity factor meant. In the prior art this start quantity factor for Direct-injection four-cylinder gasoline engines with 1.4 to 1.6 liters Displacement at 2.3 to 3.3. At a starting amount factor of 2.6 would thus a according to the invention 30% reduced starting flow factor 2.6 - 0.3 · (2.6 - 1) = 2.12 accept. Such a control leads experience with fuels commercial quality always still to a fast and steady run up and down the danger of overspeeding over the Idle speed addition. At very low starting temperatures (-50 to -10 ° C) it is preferably, the starting amount factor over the prior art even not or only to a degree of 10% to reduce. In the same way is preferably at engine temperatures in the range of 50 to 100 ° C method. This should at low temperatures a minimum amount of fuel supplied secure or unnecessarily high at high starting temperatures Prevent falling of the already very low starting quantity factor.

The Duration of the monitoring intervals while the first starting phase is determined by the engine temperature, the number of cylinders and / or one of the starter setpoint speed dependent time threshold determined. The Duration of the monitoring interval while The second start phase is determined by the duration of the monitoring interval of the first Starting phase and the number of injections from start to finish End of the first start phase determined. These measures too support a fast and steady startup the internal combustion engine. The amount of fuel supplied can be especially exactly the actual needs while be adapted to the starting process and the wall film formation is pushed back as far as possible.

An amount of the starting quantity factor during the second starting phase is determined as a function of a deviation of the idling speed from the current engine speed, a current engine speed change, a course of the speed change since the start of the start and / or a previous starting quantity factor. This should take into account the fact that after the first at least partially expiring combustion in which the injected fuel at least 30% participates in the combustion process, the component temperatures increase rapidly. As a result, increasingly evaporates the fuel wall film and participates in the combustion and torque formation. Therefore, in particular, the starting amount factor can be reduced if the speed change is higher than a target value or the engine speed is already close to the idling speed. On the other hand, the starting amount factor may be increased when the speed change is lower than a target value, to a start delay or even a start break to prevent. A characteristic of the change of the starting quantity factor can also be carried out by taking into account previous starting quantity factors from the viewpoint of the most uniform and rapid termination of the starting process.

Farther It is preferred that the starting quantity factor by specifying a maximum Start quantity factor is limited. The maximum starting quantity factor in particular depending of parameters such as the engine temperature, the number of engine revolutions and the elapsed time since starting the booting process already amount of fuel supplied and / or engine speed. By the limitation the starting quantity factor also becomes an oversteer and / or a "run-down" of the engine avoided.

• (a) während der ersten z Einspritzvorgänge ein Startmengenfaktor ausgegeben wird, wobei z der Zylinderzahl der Verbrennungskraftmaschine entspricht,
• (b) während der nachfolgenden x Einspritzvorgänge ein gegenüber den ersten z Einspritzvorgängen abgesenkter Startmengenfaktor ausgegeben wird, solange keine Hochlauferkennung angezeigt wird,
• (c) während der nachfolgenden zumindest z Einspritzvorgänge ein gegenüber den ersten z Einspritzvorgängen angehobener Startmengenfaktor ausgegeben wird, solange keine Hochlauferkennung angezeigt wird und
• (d) während der nachfolgenden Einspritzvorgänge ein gegenüber (c) abgesenkter Startmengenfaktor ausgegeben wird, solange keine Hochlauferkennung angezeigt wird.

Furthermore, it is preferred if in the first starting phase

• (a) a starting quantity factor is output during the first z injection processes, where z corresponds to the number of cylinders of the internal combustion engine,
• (b) during the following x injection processes, a starting quantity factor reduced compared to the first z injection events is output, as long as no run-up detection is indicated,
• (C) during the subsequent at least z injection events, a starting quantity factor raised in relation to the first z injection events is output as long as no run-up detection is indicated and
• (D) during the subsequent injection events a compared with (c) lowered starting quantity factor is output as long as no run-up detection is displayed.

Prefers in particular, x is between 0.25 times and 2 times the number of cylinders is, in particular 0.4 to 0.7 times the number of cylinders is. In this way, the starting amount factor over the conventional process management be lowered even further.

The Method is preferably used when the internal combustion engine a gasoline engine, in particular a direct injection gasoline engine, is. Preferably, the use of the method is also in self-igniting Internal combustion engines (diesel).

Further advantageous embodiments are the subject of the remaining dependent claims.

The Invention will be described below in embodiments with reference to a associated Drawing closer explained.

The single FIGURE shows a schematic flow diagram, as it can be used to control a starting process of an internal combustion engine. The starting process is divided into two different starting phases, which in turn can be divided into any number of injection operations i. In order to achieve a first successful ignition at the still low engine temperatures T _M , an amount of fuel supplied is increased by a starting amount factor F _i . 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 is at least quantitatively controllable. Coordination of individual, participating in the starting process units can be done in a known manner via an engine control unit.

After starting, the engine is first accelerated by the starter until a first threshold for the engine speed n is reached. From this point the fuel supply is absorbed by injection. When this first threshold value is reached, the fuel supply is released in such a way that initially a first, low starting quantity factor F _{i is} specified. With the beginning of this first injection process (i = 1), a first monitoring interval dt _{1 is also} started. In the monitoring interval dt ₁ is checked by means of a run-up detection HE whether already a successful run-up of the engine is detected. Such, known per se ramp-up detection tracks a speed change in a predetermined time interval. If the speed change exceeds a specifiable threshold for the engine speed n, then a successful startup of the engine is faked.

The starting quantity factor F _{i of} the respective injection process i is dependent on the engine temperature T _M and the possibly preceding start quantity factor F _{i-1 in} terms of its height. In particular, when establishing a first starting quantity factor F _i (with i = 1), it has proved to be advantageous to take into account a historical course τ of preceding starting operations. If, for example, a startup of the engine has already been indicated in the preceding start-up processes directly at the beginning of the first start phase, then it makes sense to reduce the start quantity factor F _i . In this way, an influence of changing fuel qualities and a drifting of the parameters important in the starting process can be compensated for at an early stage with increasing vehicle life.

For each new injection process i, the starting quantity factor F _{i is} newly determined in the manner mentioned above. It has proved to be particularly advantageous to set the starting quantity factor F _i for the first z in spraying operations - where z corresponds to a cylinder number Z - to keep constant and only then make a reduction of the starting quantity factor F _i .

At engine temperatures in the range of 15 to 30 ° C, a particularly uniform and associated with low fuel consumption and total emission starting process can be performed when the starting amount factor F _i in the first start phase by 10 to 70%, in particular by 20 to 50%, is reduced. At very low temperatures, in particular in the range of -50 to -100 ° C, the starting amount factor F _i is reduced by only 0 to 10% in order to ensure starting of the engine. At temperatures of 50 to 100 ° C, a very low billing is chosen, in which the starting quantity factor F _{i is} limited to a range of 0 to 10%.

A particularly favorable and low-emission engine start is characterized in that at the latest with the (z + 1) -sten injection process starts the run-up. It is therefore advantageous, after the first z injection processes, to initially provide a lowered start quantity factor F _i for a number of x further injection events. Ideal values for x are between 0.25 · z and 2 · z, in particular 0.4 to 0.7 · z. If no run-up occurs until the (z + x) -st injection process, starting from the (z + x + 1) -th injection process, a start quantity factor F _{i which is} significantly increased compared to F _i (with i ≦ z) is calculated. This ensures that a run-up can be initiated even with unfavorable fuels or poor engine conditions. It may further be provided, after a total of d injection operations, again to provide a lowering of the starting quantity factor F _i from its then higher level, wherein d may assume a value between z + x + 1 and z + x + z + x.

The increase can be limited during the entire starting process by specifying a maximum starting quantity factor. The maximum starting amount factor is intended to prevent excessive wall film formation and may be determined as a function of the engine temperature T _M , a number of engine revolutions or injection events since the start of the starting process, a time interval since the start of the starting process, an already supplied fuel quantity and / or the engine speed n.

If no run-up is detected after a predefinable maximum number i _{1, max} of injection processes, it is advantageous to stop the starting process in order to protect the battery and starting system. The maximum number i _{1, max of} the injection events is determined as a function of a previously determined duration of the monitoring interval dt ₁ . The duration of the monitoring interval dt ₁ is again essentially a function of T _M and is preferably above (z + x + z + x) and below a time threshold y, y preferably being selected such that the starting process depends on the starter setpoint speed after 20 to 90 s, optimally after approx. 30 to 60 s, without ramp-up detection.

As soon as the run-up detection HE signals a run-up of the motor, the magnitude of the start quantity factor F _{i is} subjected to other factors in the second start phase. In addition to a deviation δn of a target idling speed n ₀ from the current engine speed n, a current speed change dn and / or a course of the speed change Δn since the start of the start, the height of a preceding starting quantity factor F _i-1 can again be included. It is assumed in this case that the fuel saved in the first starting phase participates only partially in the combustion process and the remainder is deposited predominantly on the cylinder walls, the piston crown, the valve plates, the cylinder head (and in the intake manifold). After the first ignition and combustion, the engine temperature T _M increases rapidly, so that an increasing contribution of this fuel film for torque formation and combustion occurs.

The starting quantity factor F _i is now changed or maintained for each new injection process of the subsequent second start phase until a successful achievement of the idle speed n _{0 is} indicated by an idle detection LE and thus a successful engine start. After successful engine start the starting quantity factor F _{i is} reduced to 1, unless for example by the idle controller in a known manner, a mixture enrichment is required.

An override, ie an unnecessarily high fuel input, should be prevented by the targeted influencing of the starting quantity factor F _i . For this purpose, the starting quantity factor F _{i is taken} back when the engine speed n is close to the idling speed n ₀ . Similarly, the start amount factor F _{i can be} withdrawn if the speed change .DELTA.n is higher than a speed-dependent target specification. However, if the speed change .DELTA.n lower than another target specification, the start quantity factor F _i is raised to prevent a start delay or even a take-off. A duration of the second monitoring interval dt ₂ is essentially determined by the duration of the monitoring interval dt ₁ and the number m _{i1 of} the already performed injections since the start of the start until the initiation of the second start phase. Along with this, a maximum number i _{2, max} of injection events i of the second start phase is determined. If the start up to the injection process i _{2, max is} not completed by idle detection LE, a start aborted. After successful engine start, the starting quantity factor F _{i is} withdrawn or other engine control functions assume the requirement of a mixture enrichment.

dn

current Speed change

dt ₁ , dt ₂

duration the monitoring intervals the first and second start phase

F _i

Start quantity factor

F _i-1

Start quantity factor, previous

HE

Up detection Injection process

i _{1, max}

maximum Number of injections in the first start phase

i _{2, max}

maximum Number of injections in the second start phase

LE

Idle connection

m _i1

number the injection processes since the start until the start of the second start phase

n

Engine speed

n ₀

Idle speed

T _M

engine temperature

y

Time threshold for the monitoring interval dt ₁

Z

number of cylinders

.DELTA.n

time Speed change

.DELTA.n

Deviation of the engine speed n from the idle speed n ₀

τ

historical History of previous starts

Claims (18)

Method for determining a quantity of fuel supplied during a starting process of an internal combustion engine, in which the supplied fuel quantity is changed by a starting quantity factor (F _i ), characterized in that (a) the starting process of the internal combustion engine in two starting phases with any number of individual injection events (i) and for each injection event (i) a start quantity factor (F _i ) is determined, (b) the start quantity factor (F _i ) is reduced or maintained in each new injection operation (i) of the first start phase, until a successful startup of the internal combustion engine by a Run-up detection (HE) is displayed, wherein a height of the start quantity factor (F _i ) during the first start phase in dependence on an engine temperature (T _M ), a height of a predetermined start quantity factor (F _i-1 ), a cylinder number (Z) and / or a historical history (τ) of previous starts fe and determining the duration of a monitoring interval (dt ₁ ) of the first starting phase by the engine temperature (T _M ), the number of cylinders (z) and / or a time threshold (y) dependent on a starter setpoint speed, (c) the starting quantity factor (F _i ) is changed or maintained in each new injection operation (i) of the subsequent second starting phase until a successful reaching of an idling speed (n ₀ ) is indicated (successful engine start), wherein a height of the starting quantity factor (F _i ) during the second starting phase as a function of a deviation (δn) of the idle speed (n ₀ ) to the current engine speed (n), a current speed change (dn), a course of the speed change (Δn) since the start of the start and / or a previous starting quantity factor (F _i-1 ) and the duration of a monitoring interval (dt ₂ ) of the second starting phase by the duration of the monitoring interval (dt ₁ ) of the first starting phase and a number (m _i1 ) of the injection events (i) is determined from the start to the end of the first starting phase, and (d) the starting quantity factor (F _i ) is withdrawn after successful engine start or other engine control functions take over the request for a mixture enrichment. A method according to claim 1, characterized in that the starting quantity factor (F _i ) at engine temperatures (T _M ) in the range of 15 to 30 ° C is reduced by 10 to 70%. A method according to claim 2, characterized in that the starting quantity factor (F _i ) at engine temperatures (T _M ) in the range of 15 to 30 ° C is reduced by 20 to 50%. A method according to claim 1, characterized in that the starting quantity factor (F _i ) at engine temperatures (T _M ) in the range of -50 to -10 ° C is reduced by 0 to 10%. A method according to claim 1, characterized in that the starting amount factor (F _i ) at engine temperatures (T _M ) in the range of 50 to 100 ° C is reduced by 0 to 10%. Method according to one of claims 1 to 5, characterized that as a run-up detection (HE), the exceeding of a predetermined speed threshold and / or a predetermined speed-dependent temporal speed change is used. Method according to one of claims 1 to 6, characterized in that the achievement of the idle speed (n ₀ ) by an idle detection (LE) is displayed. Method according to claim 7, characterized in that in that the first intervention of an idle controller is the idle detection (LE) is used. A method according to claim 1, characterized in that the starting quantity factor (F _i ) zurückge is taken when the engine speed (n) is close to the idle speed (n ₀ ). A method according to claim 1, characterized in that the starting quantity factor (F _i ) is withdrawn if the speed change (Δn) is higher than a speed-dependent target specification. A method according to claim 1, characterized in that the starting amount factor (F _i ) is raised when the speed change (Δn) is lower than a speed-dependent target specification. Method according to one of claims 1 to 11, characterized in that the starting quantity factor (F _i ) is limited by specifying a maximum starting quantity factor. A method according to claim 12, characterized in that the maximum starting amount factor in dependence on the engine temperature (T _M ), a number of engine revolutions since the start of the starting process, a time interval since the start of the starting process, an already supplied amount of fuel and / or the engine speed (n) is determined. Method according to one of claims 1 to 13, characterized in that after exceeding of the duration of the monitoring intervals (dt ₁ , dt ₂ ) dependent maximum number (i _{1, max} , i _{2, max} ) of the injection events (i), a start abort occurs , Method according to one of claims 1 to 14, characterized in that (a) during the first z injection operations, a starting amount factor (F _i ) is output, wherein z corresponds to the number of cylinders (Z) of the internal combustion engine, (b) during the subsequent x injection operations compared to the first such injection events lowered starting quantity factor (F _i) is output, as long as no ramp-up detection is displayed (HE), (c) during the subsequent at least for injection processes one compared to the first such injection events raised starting quantity factor (F _i) is output, as long as no ramp-up detection (HE) is displayed and (d) during the subsequent injection operations, a reduced compared to (c) start quantity factor (F _i ) is output as long as no run-up detection (HE) is displayed. Method according to claim 15, characterized in that that x is between 0.25 times and 2 times the number of cylinders (Z), in particular 0.4 to 0.7 times the number of cylinders (Z) is. Use of a method for controlling a supplied Fuel quantity during a starting process of an internal combustion engine after a the claims 1 to 16, characterized in that the internal combustion engine a gasoline engine, in particular a direct injection, is. Use of a method for controlling a supplied Fuel quantity during a starting process of an internal combustion engine after a the claims 1 to 16, characterized in that the internal combustion engine a diesel engine is.