JP2001271689A - Operating method for internal combustion engine, control element for internal combustion engine control device, the internal combustion engine and internal combustion engine control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent wetting of an ignition plug for a repeated cold start period and to further ensure the operating method for an internal combustion engine 1 in an automobile for injecting fuel to a combustion chamber 4 of the internal combustion engine 1 in a compression phase (first operating mode and in an intake phase (second operating mode), with an injection start t-EB in the area of an top dead center OT of the intake phase at the time of the cold start of the internal combustion engine 1. SOLUTION: At repeated cold starts, the injection start is shifted to a time which is delayed comparatively, when compound to the cold start.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method of operating an internal combustion engine, for example in a motor vehicle, in which fuel is supplied in a first operating mode during a compression phase and in a second operating mode during an intake phase. Inject into the combustion chamber of the internal combustion engine, where in the case of a cold start of the internal combustion engine, the injection start is in the region of the top dead center of the intake phase,
Method of the form. The invention furthermore relates, for example, to an internal combustion engine of a motor vehicle, comprising a combustion chamber, wherein the combustion chamber has a fuel in a first operating mode during a compression phase and in a second operating mode during an intake phase. Is to be injected, equipped with a control device,
The control device relates to an internal combustion engine of the type in which, in the case of a cold start of the internal combustion engine, the injection start is adjusted and set in the region of the top dead center of the intake phase. The invention furthermore relates to a control device for such an internal combustion engine.

[0002]

2. Description of the Prior Art Systems of this type for injecting fuel directly into the combustion chamber of an internal combustion engine are generally known. In this case, a distinction is made between so-called stratified combustion as the first operating mode and so-called homogeneous combustion as the second operating mode. Stratified combustion is used especially when the load is relatively low, while homogeneous combustion is used when the load on the internal combustion engine is relatively high.

[0003] In stratified combustion, fuel is injected into the combustion chamber during the compression phase of the internal combustion engine such that, at the time of ignition, a fuel cloud is created immediately around the spark plug. This injection can be performed in different ways.
In other words, the injected fuel cloud may already be at the spark plug during the injection or directly after the injection and thus be ignited. It is also possible for the injected fuel cloud to be guided to the spark plug by the transfer of charge and then ignited gradually.
In both combustion methods, there is no homogeneous fuel distribution and a stratification is formed.

[0004] The advantage of stratified combustion is that a relatively small applied load can be driven by the internal combustion engine with a very small amount of fuel. However, relatively large loads cannot be satisfied by stratified combustion.

In homogeneous combustion, which is designed for relatively large loads of this type, the fuel is injected during the intake phase of the internal combustion engine, so that vortexing and therefore the distribution of the fuel in the combustion chamber takes place without problems. Can be. To this extent, homogeneous combustion is largely in the conventional way,
It corresponds to the method of operation of the internal combustion engine, in which fuel is injected into the intake pipe. If necessary, homogeneous combustion can be used even at relatively low loads.

[0006] In stratified combustion, the throttle flap is opened largely to the intake pipe leading to the combustion chamber and combustion is controlled and / or regulated substantially only by the quantity of fuel to be injected. In homogeneous combustion, the throttle flap is opened or closed depending on the required moment and the fuel quantity to be injected is controlled and / or regulated as a function of the intake air quantity.

In the two modes of operation, stratified charge combustion and homogeneous charge combustion, the fuel mass to be injected additionally depends on a number of other actuating variables, taking into account fuel savings, emission reductions, etc. Is controlled and / or adjusted to an appropriate value. The control and / or regulation is performed by the control unit for the internal combustion engine and is different in both operating modes.

[0008] Fuel is commonly used in direct injection internal combustion engines.
The fuel is injected into the combustion chamber of the internal combustion engine via the high-pressure injection valve. In each case, a high-pressure injection valve and a spark plug protrude into the combustion chamber of the internal combustion engine. During a cold start of the internal combustion engine, especially at low temperatures, the amount of fuel injected into the combustion chamber must be significantly higher than in a warm-up internal combustion engine. This is in particular for the following reasons: o A sufficient quantity of fuel components which are easy to boil for the ignitable fuel / air mixture at the temperature occurring must be provided.

[0009] Fuel losses which decrease with the heating of the internal combustion engine must be compensated for (for example, fuel carried in oil).

[0010] A fuel wall film must be formed (in the case of intake pipe injection, especially in the intake pipe, but also in the combustion chamber; in the case of direct gasoline injection, only in the combustion chamber).

In order to be able to inject such an increased fuel quantity during a cold start, the start of injection is in the region of the top dead center of the intake phase during a cold start. The injection then generally lasts until the ignition of the fuel cloud or between the top dead centers of the ignition phase. During operation of the internal combustion engine, the temperature of the internal combustion engine rises slowly and the amount of fuel to be injected into the combustion chamber can be reduced as the operating temperature increases. The amount of fuel to be injected can be reduced by increasing the operating temperature of the internal combustion engine even at the time of repeated start. Even in the case of repeated cold starts when the temperature of the internal combustion engine is below the operating temperature, the amount of fuel to be injected can be reduced. This is because it is no longer necessary to form a fuel wall film on the intake pipe and / or the combustion chamber. In the case of repeated cold starts, there is usually still a fuel wall film formed during the preceding cold start and the subsequent operation of the internal combustion engine.

In order to reduce the quantity of fuel to be injected, according to the prior art, the end of the injection is shifted to a relatively early point in time, so that the injection is already ended before the top dead center of the ignition phase. The injection still remains in the region of the top dead center of the intake phase.

That is, in the prior art, the start of the injection is in the region of the top dead center of the intake phase both at the time of the cold start and at the time of the repeated start. This means that the piston which can be reciprocated in the cylinder of the internal combustion engine is in the immediate vicinity of the high-pressure injection valve and the spark plug at the start of injection.
The probability that a large part of the fuel quantity to be injected directly hits the piston face and thus does not evaporate sufficiently is very high. In addition, some of the fuel to be injected may bounce off the piston face and wet the spark plug. In the case of repeated cold starts, the process is repeated according to the prior art and the amount of fuel wetting the spark plug is:
The spark plug can be so large that the spark can no longer be generated. If this occurs in a plurality of cylinders of the internal combustion engine, the internal combustion engine can no longer be started until the spark plug is dry again.

[0014]

SUMMARY OF THE INVENTION It is an object of the present invention to prevent spark plug wetting during repeated cold starts and to enable reliable repeated cold starts of the internal combustion engine.

[0015]

SUMMARY OF THE INVENTION In order to solve this problem, the present invention starts from a method of operating an internal combustion engine of the type described at the outset, in which the injection start is repeated in a cold start compared to a cold start. It is proposed to shift to a relatively late point in time.

According to the present invention, in the repeated cold start, although the temperature of the internal combustion engine moves to a relatively low region in the same manner as in the case of the cold start, the preceding cold start is repeated. The starting point is that a smaller amount of fuel may be injected into the combustion chamber of the internal combustion engine than during a cold start. The main reason for this is that during the cold start and the subsequent operation of the internal combustion engine, a combustion wall film has already formed on the intake pipe and / or the combustion chamber of the internal combustion engine. This combustion wall film is still maintained for a predetermined time interval after the internal combustion engine is shut down and does not need to be formed again at repeated cold starts.

Another factor in reducing the amount of fuel to be injected into the combustion chamber is that the temperature of the internal combustion engine, especially of the combustion chamber, which is repeated, increases slightly but slightly more than during the cold start. Is to be. This makes it possible to use only a small amount of the fuel component that easily boils with respect to the mixture having ignition capability. Furthermore, the fuel loss to be compensated for by the fuel to be additionally injected decreases as the heating of the internal combustion engine increases.

According to the invention, the reduction in the amount of fuel to be injected during repeated cold starts is realized by shifting the start of injection to a relatively late point in time. That is, the injection is started at a relatively late point in time when the piston reciprocating in the cylinder has already moved again away from the high-pressure injection valve and the spark plug. That is, at the start of injection, the distance between the piston on one side and the high-pressure injection valve and the spark plug on the other is enlarged. Thereby, it can be prevented that most of the fuel amount injected into the combustion chamber directly hits the piston surface and does not evaporate sufficiently. Furthermore, the probability that part of the injected fuel will be bounced off by the piston face and wet the spark plug is correspondingly reduced. In this way, the safety of the start of the internal combustion engine in the repeated cold start can be definitely increased. At the same time, fuel savings and improved exhaust emissions can be obtained.

[0019]

In an advantageous embodiment of the invention, during repeated cold starts, as the temperature of the combustion chamber rises, the amount of fuel injected is reduced at a point in time which is relatively late after the start of injection. It is proposed to reduce by shifting to Unlike the prior art, where the fuel quantity is realized by a relatively early termination of the injection, according to the invention,
The reduction in the amount of fuel to be injected is realized by a relatively late start of the injection. That is, as the temperature of the combustion chamber of the internal combustion engine increases, the probability that a part of the fuel amount to be injected into the combustion chamber directly hits the piston face and does not evaporate sufficiently or is rebounded by the piston face and the spark plug is wetted. Is further reduced.

According to an advantageous embodiment of the invention, a repeated cold start is detected if there is a repeated start and the temperature of the combustion chamber is below a predetermined temperature threshold. It is suggested that: The temperature threshold is below the operating temperature of the internal combustion engine. Particularly when the ambient temperature is relatively low, the temperature threshold is above the temperature of the internal combustion engine after a cold start.

If the preceding start phase is within a predetermined time threshold and the minimum number of combustions which can be predetermined in the start phase has been performed,
There is an advantageously repeated start. If the preceding start process is above a predeterminable time threshold, a new start and a repeated start are not considered. There are several indicators for the minimum number of combustions: temperature rise in the combustion chamber, pressure rise in the cylinder, increase in the speed of the internal combustion engine, the amount of unburned fuel in the exhaust gas and the λ value of the λ sensor ( Exhaust gas or for individual cylinders).

The time threshold is advantageously predetermined in dependence on the temperature of the combustion chamber. The minimum number of combustions which can be determined in advance is also preferably determined in dependence on the temperature of the combustion chamber.

It is of particular importance if the method according to the invention is implemented in the form of a control element provided, for example, for a control device for an internal combustion engine of a motor vehicle. The control element stores a program which can be executed on a computer of the control device, for example a microprocessor, and which is suitable for carrying out the method according to the invention. Thus, in this case, the invention is realized by means of a program stored in the control element, so that the control element comprising the program is provided in a manner similar to the way the program is suitable for its implementation. 1 illustrates the present invention. Control elements such as lead
An electrical memory medium such as only memory or flash memory is used.

As a further solution to the problem of the invention, starting from an internal combustion engine of the type described at the outset, in the case of repeated cold starts, the control device makes the injection start relatively short compared to the cold start. It is proposed to shift to a late point in time.

Furthermore, as a further solution to the problem of the invention, starting from a control device of the type described at the outset, when the control device is repeatedly cold-started, the injection start is compared to the cold start. It is proposed to shift to a relatively late point in time.

Further features, possible uses and advantages of the invention will be apparent from the following description of an embodiment of the invention, as illustrated in the drawings. All of the features described or illustrated in themselves or in any combination form the subject of the present invention, irrespective of the subject matter of the claims or of their dependent relationships, and irrespective of their construction or presentation in the description or drawings. are doing.

[0027]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, the present invention will be described in detail with reference to the illustrated embodiments.

FIG. 1 shows a direct injection type internal combustion engine 1 of a motor vehicle. Here, piston 2 is cylinder 3
It is designed to reciprocate inside. The cylinder 3 has a combustion chamber 4. The combustion chamber is formed, inter alia, by a piston 2, an inlet valve 5 and an outlet valve 6. The inlet valve 5 is connected to a suction pipe 7 and the outlet valve 6 is connected to an exhaust pipe 8.

In the region of the inlet valve 5 and the outlet valve 6, a high-pressure injection valve 9 and a spark plug 10 protrude into the combustion chamber 4. Fuel can be injected into the combustion chamber 4 through the high-pressure injection valve 9. The fuel in the combustion chamber 4 can be ignited by the ignition plug 10.

The piston 2 is converted into a reciprocating motion by the combustion of fuel in the combustion chamber 4. This movement is transmitted to a crankshaft (not shown) and causes a torque to be built therein.

When the internal combustion engine 1 is cold or during a cold start or a cold start (simply referred to as a cold start), especially when the temperature is low, the amount of fuel injected into the combustion chamber 4 depends on the warm-up operation. Must be significantly increased compared to internal combustion engines. This can be attributed, inter alia, to the following: o A sufficient quantity of readily boilable fuel components must be provided for the ignitable fuel-air mixture at the temperature occurring. .

O The fuel loss, which decreases as the heating of the internal combustion engine increases, must be compensated (for example, fuel carried in oil).

The fuel wall film in the combustion chamber 4 must be formed.

In order to be able to use such an increased fuel quantity during a cold start, the injection start t at the cold start EB is in the region of the top dead center OT of the intake phase. The injection then lasts until the ignition of the cloud fuel (combustion cloud) or the top dead center OT of the ignition phase. During operation of the internal combustion engine 1, its temperature rises slowly and the amount of fuel to be injected into the combustion chamber 4 can be reduced as the operating temperature rises.

That is, at the time of cold start, injection start t
EB is in the region of the top dead center OT of the intake phase. This means that the piston 2 is immediately adjacent to the high-pressure injection valve 9 and the spark plug 10 at the start of injection in the cylinder 3. As a result, the probability that the majority of the injected fuel quantity directly hits the piston surface and therefore does not evaporate sufficiently is very high. Further, a part of the injected fuel rebounds from the piston face and the spark plug 10
Could get wet. According to the prior art, this process is repeated at each repeated cold start, and the amount of fuel that wets the spark plug 10 can be so large that the spark plug 10 can no longer generate an ignition spark.
If this occurs in the multiple cylinders 3 of the internal combustion engine 1, the internal combustion engine 1 can no longer be started until the spark plug 3 is dry again.

In order to prevent the spark plug 10 from getting wet during repeated cold starts and making it difficult to start the internal combustion engine 1, the injection start t at repeated cold starts is started. The EB is shifted in a direction at a time point later than the cold start.

According to the present invention, although the temperature of the internal combustion engine 1 in the repeated cold start is in a relatively low region as in the case of the cold start, the preceding cold start in the repeated cold start is performed. This is because it is only necessary to inject a smaller amount of fuel into the combustion chamber 4 of the internal combustion engine 1 than in the case of the intermittent start. The reason for this is, in particular,
During the cold start and during the subsequent operation of the internal combustion engine 1, the combustion chamber 4 of the internal combustion engine 1 already has a fuel wall film. Such a fuel wall film is used for the internal combustion engine 1.
It remains in place for a predetermined duration after the shut-off, and does not need to be reformed again in repeated cold starts. The fact that the temperature of the internal combustion engine 1, especially the temperature of the combustion chamber 4 is slightly increased at the time of repeated cold start as compared with the cold start is another reason that the amount of fuel to be injected into the combustion chamber 4 is reduced. It is a factor.
At the start of a new start, the start of injection is, for example, a temperature of -3.
It is reduced from 360 ° crank angle KW at 0 ° C. to 280 ° KW at + 10 ° C. In the repeated start, the injection start is, for example, 3 when the temperature is −30 ° C.
280 ° at + 10 ° C from 20 ° crank angle KW
It is reduced to KW. As a result, only a smaller amount of readily boiling fuel components can be used for the ignitable mixture. Furthermore, the fuel loss which has to be compensated by the additionally injected fuel decreases as the heating of the internal combustion engine 1 increases.

According to the present invention, this reduction in the amount of fuel to be injected during the repeated cold start is achieved according to the invention. This is achieved by shifting the EB towards a relatively late point in time. That is, injection start t EB is
It is at a relatively late point in time that the piston 2 reciprocating in the cylinder 3 is already moving away from the high-pressure injector 9 and the spark plug 10 again. Therefore, at the start of the injection, the distance between the piston 2 and the spark plug 10 is also increased. Thus, it is possible to prevent a large portion of the fuel injected into the combustion chamber 4 from directly hitting the piston surface and not sufficiently evaporating. Further, part of the injected fuel rebounds from the piston surface, and the spark plug 10
The probability of wetting is significantly reduced. In this way, the start safety of the internal combustion engine 1 at the time of repeated cold start can be definitely increased. At the same time, fuel savings and better emissions can be achieved.

At the time of repeated cold start, as the temperature of the combustion chamber 4 rises, the injection start t The amount of fuel injected is reduced by further shifting the EB toward the later point in time. That is, as the temperature of the combustion chamber 4 of the internal combustion engine 1 increases, a part of the amount of fuel injected into the combustion chamber 4 directly hits the piston surface and does not sufficiently evaporate or rebounds from the piston surface, and the ignition plug 10 The probability of wetting is further reduced.

A sequence flow chart of the method of the present invention is shown in FIG. The method starts at function block 20. According to the invention, the temperature T of the combustion chamber 4 can be determined in advance by a temperature threshold T sch
When the value is below w (question block 21) and a repeated start occurs, it is assumed that there is a repeated cold start. The temperature threshold is generally below the operating temperature of the internal combustion engine 1, but if the ambient temperature is very low,
It is above the temperature of the internal combustion engine 1 after a cold start.
In this embodiment, the temperature threshold T schw is 20
° C range.

According to the invention, the repetitive start is a time threshold t at which the preceding start process can be predetermined. the minimum number of times V which is in schw (question block 22) and can be predetermined in the starting process When the combustion of min has been performed (interrogation block 23), it is determined to be present. In this embodiment, the time threshold t schw is in the area of 5 min. If the preceding starting process was performed more than 5 minutes ago,
It is considered a new start, not a repeated start.

Minimum number of times V There are a number of indicators to determine if a min burn has been performed:
Temperature rise in the combustion chamber 4, pressure rise in the cylinder 3, increase in the number of revolutions of the internal combustion engine 1, the amount of unburned fuel in the exhaust gas and the lambda value of the lambda sensor (whole exhaust gas or individual cylinder 3).

Time threshold t schw and minimum number
V min combustion depends on the temperature T of the combustion chamber 4 beforehand.
Can be determined. If a repeat start exists,
In function block 24, injection start t EB is cold
It is shifted toward the point of the delay compared to the start. So
If not, in the function block 25, the injection start t EB
Is selected in the same manner as in a normal cold start. Function bro
At block 26, the method ends.

The method according to the invention is used in particular for internal combustion engines 1 of motor vehicles.
It is particularly important to implement this in the form of a control element provided for the control device 11. In that case, a program is stored in the control element. The program is executed on a computer of the control unit 11, in particular a microprocessor, and is suitable for implementing the method according to the invention. That is, in this case, the present invention is implemented by the program stored in the control element, and the control element having the program implements the present invention in the same manner as a method suitable for executing the program. Things. In particular, read-only memory or flash memory
An electronic memory medium such as a memory can be used.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of an internal combustion engine of an advantageous embodiment of the present invention.

FIG. 2 is a chart showing the sequence of the method of the invention according to an advantageous embodiment of the invention.

[Explanation of symbols]

1 internal combustion engine, 2 piston, 3 cylinder, 4
Combustion chamber, 5 Inlet valve, 6 Outlet valve, 9 High pressure injection valve, 10 Spark plug, 11 Control device

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (reference) F02D 45/00 312 F02D 45/00 312B (72) Inventor Rüdiger Weiss Germany Metzingen at Halmstrasse 23

Claims (9)

[Claims] 1. A method of operating an internal combustion engine (1) of a motor vehicle, for example, wherein fuel is supplied in a first operating mode during a compression phase and in a second operating mode during an intake phase. The fuel is injected into the combustion chamber (4) of (1), and when the internal combustion engine (1) is cold started,
Start of injection (t EB) is the top dead center (OT) of the intake phase
At the time of repeated cold start, the injection start (t EB) is shifted to a point in time that is relatively late compared to the cold start. 2. At the time of repeated cold start, as the temperature (T) of the combustion chamber (4) rises, the amount of fuel to be injected is reduced by the injection start (t). 2. The method according to claim 1, wherein EB) is reduced by shifting to a later point in time. 3. A temperature threshold (T) wherein there is a repeated start and the temperature (T) of the combustion chamber (4) is predetermined. 3. The method as claimed in claim 1, wherein a repeated cold start is detected if it is below schw). 4. A preceding starting process is predetermined.
Time threshold (t schw) and start over
The minimum number of times (V m
in) If the combustion is performed, repeated start
4. The method of claim 3, wherein 5. The time threshold (t) 5. The method according to claim 4, wherein the step (schw) is predetermined depending on the temperature (T) of the combustion chamber (4). 6. The minimum number of times (V
6. The method as claimed in claim 4, wherein the combustion of the combustion chamber is determined in advance as a function of the temperature of the combustion chamber. 7. A control element, for example a read-only memory or a flash memory, for a control device (11) for an internal combustion engine (1) of a motor vehicle, for example, wherein the control element includes the control device (11). calculator,
A control element storing a program executable on a microprocessor, for example, and suitable for performing the method according to one of claims 1 to 6. 8. An internal combustion engine (1) for a motor vehicle, for example, comprising a combustion chamber (4) in a first operating mode during a compression phase and during a first operation mode during an intake phase. In the operation mode 2, the fuel is injected, and a control device (11) is provided. The control device starts the injection (t) when the internal combustion engine (1) starts cold. In the internal combustion engine of the type in which EB) is adjusted and set in the region of the top dead center (OT) of the intake phase, the control device (11) performs a cold start repeatedly.
Start of injection (t An internal combustion engine characterized in that EB) is shifted to a point in time that is relatively late as compared to a cold start. 9. The control device (11) for an internal combustion engine (1) of a motor vehicle, for example, wherein the internal combustion engine (1) has a combustion chamber (4) in which the combustion chamber (4) is connected during the compression phase. In one first operating mode and in a second operating mode during the intake phase, fuel is injected and comprises a control device (11), which controls the cooling of the internal combustion engine (1). Injection start (t E
B) in a control device of the type that adjusts and sets B) in the region of the top dead center (OT) of the intake phase.
When cold start is repeated, injection is started (t).
EB) is shifted to a point in time that is relatively late as compared with the cold start.