EP1199459A2 - Method for the starting up of an internal combustion engine - Google Patents

Abstract

The invention relates to a fuel system with which the fuel is supplied under pressure from a reservoir. When starting the engine the fuel is injected in the compression phase (layer operation) and before or immediately after injection the fuel pressure is measured. Depending on whether the pressure level exceeds a set threshold layer operation is continued or cancelled.

Description

State of the art

The invention is based on a method for starting an internal combustion engine, in particular a motor vehicle, at which pressure is exerted on the fuel, and at which is the fuel in a shift operation during a Compression phase or in a homogeneous operation during injected directly into a combustion chamber during an intake phase becomes. The invention also relates to a corresponding one Internal combustion engine, a corresponding control unit as well an appropriate computer program for such Internal combustion engine.

Such a method, such Internal combustion engine, such a control unit and a such a computer program are, for example, from a known as gasoline direct injection. There will the fuel through injectors during the Intake phase or directly in during the compression phase injected the combustion chamber and burned there. For the The fuel is pre-injected Fuel accumulator pressurized. This represents the pressure on the fuel acts, and with which the fuel with it over the Injectors are injected into the combustion chambers.

When starting the internal combustion engine must in particular non-warm internal combustion engine an increased Amount of fuel is injected into the combustion chamber. This has the consequence that the pressure in the fuel accumulator can significantly reduce. This drop in pressure is still going on reinforced by the fact that when starting the internal combustion engine the pressure in the fuel accumulator may not yet be is sufficiently available and not so quickly can be built and maintained.

For the operation of the internal combustion engine in shift operation is a certain pressure acting on the fuel required. This results from the fact that in the Compression phase during the shift operation of the Fuel is injected into the combustion chamber in the combustion chamber the compression pressure rises sharply. Now the Compression pressure greater than that during injection pressure acting on the fuel, this has the undesirable consequence that the fuel to be injected into the pressure accumulator is blown back.

Due to the described drop in pressure when starting the Internal combustion engine can just blow back like this occur particularly quickly when starting.

Object and advantages of the invention

The object of the invention is a method for starting to create an internal combustion engine with which a Blow fuel back into the accumulator safely is avoided.

This task is initiated in a procedure mentioned type according to the invention solved in that the End or after an injection on the fuel acting pressure is determined, and that depending from this pressure the shift operation excluded or is allowed. In an internal combustion engine, one Control unit and a computer program of the beginning mentioned type, the task according to the invention solved.

It is therefore the one that acts on the fuel Pressure calculated at the end or after an injection is still there. This calculation is for each one Injection carried out individually. In dependence of this determined pressure, it is then decided whether that There is a risk of fuel blowing back, and whether shift operation must therefore be excluded or can be approved.

This way, for every single injection ensures that only then in shift operation can be switched when on the fuel pressure is large enough. This is not the case, switching to shift operation is excluded or an existing shift operation is switched off.

An undesirable blow back of fuel in the Fuel storage is thus reliably prevented.

In an advantageous embodiment of the invention from the before or at the beginning of the injection to the Fuel acting pressure in before injection existing fuel mass in the fuel accumulator determined. This is based on an equation performed the compressibility of the fuel considered.

In a further advantageous embodiment of the Invention is derived from the pre-injection in the Fuel storage existing fuel mass and from the Fuel mass to be injected after injection Mass of fuel present in the fuel accumulator determined. This is done by means of a difference carried out.

After that, after the injection in the Fuel storage existing fuel mass at the end or after the injection on the fuel Pressure determined. This is again done with the help of the aforementioned equation.

It is particularly advantageous if the end or after the pressure acting on the fuel a threshold pressure is compared. The Threshold pressure corresponds approximately to that pressure which is necessary for the shift operation to be carried out can be.

Thereafter, shift operation is excluded if the on End or after fuel injection acting pressure is less than the threshold pressure.

The realization of the inventive method in the form of a Computer program for a control unit Internal combustion engine, in particular a motor vehicle, is provided. The computer program is special executable on a microprocessor and for executing the method according to the invention suitable. In this case that is, the invention is implemented by the computer program, so that this computer program in the same way the Invention represents how the method for carrying it out the computer program is suitable. The computer program can be stored on an electrical storage medium be, for example on a flash memory or Read-only memory.

Other features, applications and advantages of the Invention result from the following description of embodiments of the invention shown in the figures the drawing are shown. Thereby everyone described or illustrated features for themselves or in any combination the subject of the invention, regardless of their summary in the Patent claims or their relationship and independently from their formulation or representation in the description or in the drawing.

Embodiments of the invention

Figure 1

shows a schematic block diagram of a Embodiment of an inventive Internal combustion engine, and

Figure 2

shows a schematic flow diagram of a inventive method for starting the Internal combustion engine of Figure 1.

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

In the area of the inlet valve 5 and the outlet valve 6 protrude an injection valve 9 and a spark plug 10 in the Combustion chamber 4. Fuel can be injected via the injection valve 9 the combustion chamber 4 are injected. With the spark plug 10 the fuel can be ignited in the combustion chamber 4.

In the intake pipe 7 there is a rotatable throttle valve 11 housed, through which the intake pipe 7 air can be supplied is. The amount of air supplied depends on the Angular position of the throttle valve 11 is in the exhaust pipe 8 a catalyst 12 housed, the cleaning of the exhaust gases generated by the combustion of the fuel serves.

The injection valve 9 is connected to a pressure line Fuel accumulator 13 connected. In a similar way are also the injectors of the other cylinders Internal combustion engine 1 with the fuel accumulator 13 connected. The fuel accumulator 13 is a Supply line supplied with fuel. This is a electrical and / or mechanical fuel pump provided, which is suitable to the desired pressure in to build up the fuel accumulator 13.

There is also a pressure sensor on the fuel accumulator 13 14 arranged with which the pressure in the fuel accumulator 13 is measurable. This pressure is the pressure exerted on the fuel and with which therefore the fuel via the injection valve 9 injected into the combustion chamber 3 of the internal combustion engine 1 becomes.

During operation of the internal combustion engine 1, fuel is injected into the Fuel storage 13 promoted. That fuel will via the injection valves 9 of the individual cylinders 3 in the associated combustion chambers 4 injected. With the help of Spark plugs 10 become burns in the combustion chambers 3 generated by the piston 2 in a reciprocating Movement to be moved. These movements are on transmit and exercise a crankshaft, not shown this a torque.

A control unit 15 is of input signals 16 acted upon, the operating variables measured by sensors represent the internal combustion engine 1. For example, that is Control unit 15 with the pressure sensor 14, one Air mass sensor, a lambda sensor, a speed sensor and the like connected. Furthermore, the control unit 15 connected to an accelerator pedal sensor that receives a signal generates the position of one by a driver actuated accelerator pedal and thus the requested Torque indicates. The control unit 15 generates Output signals 17 with which via actuators or actuators the behavior of the internal combustion engine 1 can be influenced can. For example, the control unit 15 with the Injector 9, the spark plug 10 and the throttle valve 11 and the like connected and generated to their Control necessary signals.

Among other things, the control device 15 is provided for the To control operating variables of the internal combustion engine 1 and / or to regulate. For example, that of the injector 9 injected into the combustion chamber 4 fuel mass from the Control unit 15, in particular with regard to a small one Fuel consumption and / or a low Controlled and / or regulated pollutant development. To for this purpose, the control unit 15 with a Microprocessor provided in a storage medium, a computer program, in particular in a flash memory has saved, which is suitable for the named Control and / or regulation to perform.

The internal combustion engine 1 of Figure 1 can in a plurality operated by operating modes. So it is possible that Internal combustion engine 1 in a homogeneous operation, one Shift operation, a homogeneous lean operation, an operation to operate with double injection and the like.

In homogeneous operation, the fuel is used during the Intake phase from the injection valve 9 directly into the Combustion chamber 4 of the internal combustion engine 1 is injected. The As a result, fuel is largely used until ignition swirls so that in the combustion chamber 4 a substantially homogeneous fuel / air mixture is created. That too generating moment is essentially about the Position of throttle valve 11 from control unit 15 set. In homogeneous operation, the operating parameters the internal combustion engine 1 controlled and / or regulated that lambda equal or at least approximately the same Is one. The homogeneous operation is particularly at full load applied.

The homogeneous lean operation largely corresponds to that Homogeneous operation, however, the lambda becomes one value set greater than one.

In shift operation, the fuel is used during the Compression phase from the injector 9 directly into the Combustion chamber 4 of the internal combustion engine 1 is injected. In order to is not homogeneous when ignited by the spark plug 10 Mixture present in the combustion chamber 4, but one Fuel stratification. The throttle valve 11 can, apart from of requirements e.g. the exhaust gas recirculation and / or the Tank ventilation, fully open and the Internal combustion engine 1 to be operated dethrottled. The torque to be generated is largely in shift operation adjusted via the fuel mass. With the The internal combustion engine 1 can operate in shifts in particular be operated at idle and at partial load.

Between the mentioned operating modes of the internal combustion engine 1 can be toggled back and forth. such Switchovers are carried out by the control unit 15.

The internal combustion engine 1 after a longer Standstill started, especially at low Temperatures injected into the combustion chamber 4 Fuel mass significantly increased. That way not just an ignitable air / fuel mixture in the Combustion chamber 4 provided, but it will also compensated for those losses of fuel caused by the entry of fuel in the engine oil and / or by the construction of a wall film made of fuel in the combustion chamber 4 arise.

The large, required during startup Fuel mass to be injected has the result that the Pressure in the fuel accumulator 13 during the Injection time is greatly reduced. This will do so further reinforced that when starting the internal combustion engine 1 the electric and / or the mechanical fuel pump is not yet able to do the fast enough required pressure in the fuel accumulator 13 generate and maintain.

If the pressure in the fuel accumulator 13 drops, then there is in shift operation, the risk that during a Injection of fuel into the combustion chamber 4 Internal combustion engine 1 the compression pressure in this Combustion chamber 4 is larger than the collapsed pressure in the Fuel storage 13. This would then have the undesirable Consequence that the fuel to be injected into the Fuel reservoir 13 is blown back.

FIG. 2 shows a method with which the control unit 15 that pressure in the Fuel storage 13 is determined, there after a Injection is still present. With the help of this pressure it is then decided whether the internal combustion engine 1 in Shift operation can be operated or not. This The procedure is particularly for the starting process Internal combustion engine 1 suitable, but can also during other operations of the same are used.

In a step 20, the pressure sensor 14 is used Pressure in the fuel accumulator 13 measured. This measurement takes place immediately before or immediately on Start of the next injection of fuel into the Combustion chamber 4.

p₁₃ = Druck im Kraftstoffspeicher 13

p₀ = Umgebungsdruck

E_Kr = Elastizitätsmodul des Kraftstoffs

ρ_Kr = Dichte des Kraftstoffs

V₁₃ = Volumen des Kraftstoffspeichers 13

m_Kr13 = Kraftstoffmasse im Kraftstoffspeicher 13

aus dem gemessenen Druck im Kraftstoffspeicher 13 auf die in demselben vorhandene Kraftstoffmasse m_Kr13 geschlossen. Hierzu wird der von dem Drucksensor 14 gemessene Druck als Druck p₁₃ eingesetzt, um dann die Gleichung nach der Kraftstoffmasse m_Kr13 aufzulösen. Der Umgebungsdruck, das Elastizitätsmodul des Kraftstoffs, die Dichte des Kraftstoffs und das Volumen des Kraftstoffspeichers 13 sind dabei bekannt oder können anderweitig gemessen oder berechnet werden.In step 21, using the equation p 13 = p 0 + E Kr x (1 - ρ Kr x (V 13 / m Kr13 )) With

p ₁₃ = pressure in the fuel accumulator 13

p ₀ = ambient pressure

E _Kr = modulus of elasticity of the fuel

ρ _Kr = density of the fuel

V ₁₃ = volume of the fuel accumulator 13

m _Kr13 = fuel _mass in the fuel _accumulator 13

from the measured pressure in the fuel _accumulator 13 the fuel _mass m _Kr13 present in the same. For this purpose, the pressure measured by pressure sensor 14 is used as pressure p ₁₃ in order to then solve the equation according to fuel _mass m _Kr13 . The ambient pressure, the elastic modulus of the fuel, the density of the fuel and the volume of the fuel accumulator 13 are known or can be measured or calculated in some other way.

In a step 22, the control unit 15 calculates the fuel mass m _{Kr to} be injected from the operating variables of the internal combustion engine 1, as has already been explained. The operating variables can be the engine temperature, the ambient temperature and the like.

In a step 23, the fuel _mass m _{Kr13 is subsequently} calculated that is still present in the fuel _{accumulator 13} after the fuel _mass m _Kr has been injected. This calculation is done according to the equation m Kr13danach = m Kr13 - m Kr

With the aid of equation (1), the pressure p ₁₃ in the fuel _reservoir 13 is then determined in a step 24 immediately after the end or immediately after the injection of the fuel _mass m _Kr into the combustion chamber 4. In this case, the mass in the fuel _accumulator 13 is no longer the fuel mass m _Kr13 present before the injection, but rather the fuel _mass m _Kr13 present after the injection. The other variables, that is to say the ambient pressure, the modulus of elasticity, etc., are either either known or can be measured or calculated in some other way.

In a step 25, the pressure p _{13 is then compared} in the fuel _accumulator 13 at the end or after the injection with a threshold value pressure p _threshold . The threshold value pressure p _threshold corresponds approximately to the pressure which is required for the stratified operation to be carried out without the risk of fuel being blown back into the fuel accumulator 13.

If the pressure p _{13 thereafter is} greater than the threshold pressure p _threshold , this means that there is still enough pressure in the fuel accumulator 13 to operate the internal combustion engine 1 in _{stratified mode} . In this case, shift operation is therefore permitted in step 26.

However, if the pressure p _{13 thereafter} is less than the threshold pressure p _threshold , this means that the pressure in the fuel _accumulator 13 is no longer sufficient to operate the internal combustion engine 1 in _{stratified mode} . In this case, in particular, there is the risk that the fuel to be injected is blown back into the fuel accumulator 13 due to the greater compression pressure in the combustion chamber 4. This is prevented by excluding shift operation in a step 27 in this case.

In the method described above, the Decision of steps 25, 26, 27 on one Injection. Alternatively, it is possible to use this procedure to extend to multiple injections. For this, as in 2, but after step 24 repeats steps 21 through 24. This repetition then refers to the next injection. through four such repetitions can be four, for example Work cycles of a certain cylinder in advance be calculated. The result is the pressure in the Fuel storage after these four work cycles. With This pressure can then affect decision making Steps 25, 26, 27 are performed.

Claims (12)

Method for starting an internal combustion engine (1), in particular a motor vehicle, in which pressure is exerted on the fuel and in which the fuel is injected directly into a combustion chamber (4) in a stratified operation during a compression phase or in a homogeneous operation during an intake phase, characterized in that the pressure acting on the fuel at the end or after an injection (p _13danach ) is determined, and in that the shift operation is excluded or permitted as a function of this pressure (p _13danach ). Method according to Claim 1, characterized in that the pressure (p ₁₃ ) acting on the fuel before or at the start of the injection is measured by a pressure sensor (14). Method according to one of claims 1 or 2, wherein a fuel accumulator (13) is provided, characterized in that from the pressure (p ₁₃ ) acting on the fuel before or at the start of the injection, one existing in the fuel accumulator (13) before the injection Fuel _mass (m _Kr13 ) is determined. Method according to one of claims 1 to 3, characterized in that a fuel mass (m _Kr ) to be injected from operating variables of the internal combustion engine (1) Method according to claims 3 and 4, characterized in that from the fuel _mass (m _Kr13 ) present before the injection in the fuel _accumulator (13) and from the fuel _mass (m _Kr ) to be injected, a fuel _mass present in the fuel _accumulator (13) after the injection (m _Kr13danach ) is determined. Method according to Claim 5, characterized in that the pressure (p _13danach ) acting at the end or after the injection is determined from the fuel _mass (m _Kr13danach ) present in the fuel _accumulator (13) after the injection. Method according to one of Claims 1 to 6, characterized in that the pressure (p _{13 thereafter} ) acting on the fuel at the end or after the injection is compared with a threshold value pressure (p _threshold ). Method according to Claim 7, characterized in that stratified operation is excluded if the pressure (p _{13 afterwards} ) acting on the fuel at the end or after the injection is less than the threshold pressure (p _threshold ). Computer program for a control device (15) of an internal combustion engine (1), in particular of a motor vehicle, characterized in that the computer program is suitable for executing a method according to one of claims 1 to 8. Computer program according to Claim 9, characterized in that the computer program is stored on an electrical storage medium, in particular on a flash memory or a read-only memory. Control device (15) for an internal combustion engine (1), in particular of a motor vehicle, wherein a pressure can be exerted on the fuel when the internal combustion engine (1) is started, and the fuel in a stratified operation during a compression phase or in a homogeneous operation during an intake phase a combustion chamber (4) can be injected, characterized in that the pressure (p _{13 thereafter} ) acting on the fuel at the end or after an injection can be determined by the control _device (15), and in that the control _device (15) as a function of this pressure (p _{13 thereafter} ) shift operation can be excluded or permitted. Internal combustion engine (1), in particular of a motor vehicle, with a control device (15), wherein pressure can be exerted on the fuel when the internal combustion engine (1) is started, and the fuel is directly in a stratified operation during a compression phase or in a homogeneous operation during an intake phase a combustion chamber (4) can be injected, characterized in that the pressure (p _{13 thereafter} ) acting on the fuel at the end or after an injection can be determined by the control _device (15), and in that the control _device (15) as a function of this pressure (p _{13 thereafter} ) shift operation can be excluded or permitted.

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