Method and device for controlling internal combustion engine

Abstract

The invention relates to a method and a device for controlling an internal combustion engine (1) having a pre-chamber spark plug (3) and a hook-shaped spark plug (4) in a combustion chamber (2). In a first operating region of the internal combustion engine (1), combustion in the combustion chamber (2) is triggered by the pre-chamber spark plug (3), and in a second operating region of the internal combustion engine, combustion is triggered by the hook-shaped spark plug (4).

Description

Technical Field

[0001] The invention relates to a method and a device for controlling an internal combustion engine according to the type of independent claims. Background Art

[0002] Methods and devices for controlling internal combustion engines having either a pre-chamber spark plug or a hook spark plug are known according to the independent claims. Such internal combustion engines are controlled in a manner adapted to the pre-chamber spark plug or the hook spark plug. Summary of the invention

[0003] Advantages of the present invention

[0004] The method according to the invention or the device according to the invention having the features of the independent claims respectively has the advantage that an optimized operation of the internal combustion engine is achieved in different operating ranges. In this case, depending on the operating range, the combustion is triggered either by a pre-chamber spark plug or by a hook spark plug. Thus, an optimized operation of the internal combustion engine is achieved for each operating range, thereby achieving advantages in terms of consumption, improved performance or reduced exhaust gases.

[0005] Further advantages and improvements are obtained by the measures of the dependent claims. The combustion is triggered by a corresponding ignition spark between the electrodes of the hook spark plug. The combustion is triggered by a pre-chamber spark plug by at least one ignition jet extending into the combustion chamber of the internal combustion engine. Depending on the operating range of the internal combustion engine, the combustion is triggered by the pre-chamber spark plug, after which the ignition spark is achieved on the hook spark plug with a time delay after the ignition jet. If the combustion is triggered by the ignition spark on the hook spark plug, the ignition jet into the combustion chamber is delayed by a time delay. By this measure, the occurrence of soot on the pre-chamber spark plug or the hook spark plug can be reduced, and the combustion can also be improved. As the first operating range of the combustion triggered by the ignition jet, it is characterized in particular by the high load and knock-prone operation of the internal combustion engine. Compared with the triggering by the ignition spark, the combustion triggered by the ignition jet reduces the knock tendency, so that the internal combustion engine can be operated with consumption advantages or increased power optimization. Alternatively, each region can be defined as a first operating region in which combustion is triggered by the ignition jet of the pre-chamber spark plug, in which combustion in the combustion chamber can be reliably triggered by the pre-chamber spark plug. Accordingly, the following operating region is defined as a second operating region in which combustion is triggered by the hook spark plug, in which combustion cannot be reliably triggered by the pre-chamber spark plug. This second operating region is characterized in particular by low loads or operation for heating the exhaust gas system of the internal combustion engine. BRIEF DESCRIPTION OF THE DRAWINGS

[0006] Exemplary embodiments of the invention are shown in the drawings and are explained in more detail in the following description.

[0007] The accompanying drawings show:

[0008] Figure 1 schematically illustrates an internal combustion engine having a pre-chamber spark plug and a hook spark plug; and

[0009] Figure 2 Show according to Figure 1 Different operating areas of internal combustion engines. DETAILED DESCRIPTION

[0010] exist Figure 1 Schematically shows an internal combustion engine 1 with a combustion chamber 2. The internal combustion engine 1 has a cylinder 11, in which a piston 12 is arranged. The free area above the piston 12 of the cylinder 11 delimits the combustion chamber 2. Through the air supply 13, air can be supplied to the combustion chamber 2 for combustion, and the exhaust gas after combustion is discharged from the combustion chamber 2 through the exhaust gas line 14. For the sake of simplicity, the corresponding valves for controlling the air supply or exhaust gas discharge are not shown in the figure. In addition, fuel is introduced into the combustion chamber 2, which forms a combustible mixture with the supplied air. The fuel is supplied to the combustion chamber 2 by injecting the fuel into the air supply 13 or directly into the combustion chamber 2. For the sake of clarity, the corresponding injection valve is not shown here. By the combustion of the fuel-air mixture in the combustion chamber 2, the pressure in the combustion chamber 2 is increased, and the pressure increase causes the piston 12 to move up and down. Therefore, this involves a common Otto internal combustion engine.

[0011] The ignition of the fuel-air mixture in the combustion chamber 2 takes place via a spark plug. Figure 1 In the combustion chamber 2, two different spark plugs are arranged, namely a hook-shaped spark plug 4 and a pre-combustion chamber spark plug 3.

[0012] The hook-shaped spark plug 4 has two (or more) electrodes 5 that extend into the combustion chamber 2. Between the two electrodes 5 of the hook-shaped spark plug 4, an ignition spark can be triggered, which ignition spark is in direct contact with the combustible fuel-air mixture in the combustion chamber 2 and thus triggers combustion in the combustion chamber 2. Since one of the electrodes 5 is configured as a hook, this spark plug with an ignition spark in direct contact with the combustible mixture in the combustion chamber is called a hook-shaped spark plug. However, alternative configurations of the electrodes 5 are also conceivable, which differ from this hook-shaped electrode configuration. Therefore, in the following, a hook-shaped spark plug is understood to be all spark plugs in which the ignition spark is in direct contact with the combustible mixture in the combustion chamber 2.

[0013] The pre-chamber spark plug 3 also has electrodes between which an ignition spark can be triggered. However, the ignition spark does not come into direct contact with the combustible mixture in the combustion chamber 2, but the electrodes are surrounded by a cover 7. The cover 7 has an opening through which a combustible fuel-air mixture reaches the interior of the cover 7, and the mixture is ignited by the ignition spark between the electrodes of the pre-chamber spark plug 3. The combustion of the fuel-air mixture in the interior of the cover 7 then causes an increase in the pressure in the interior of the cover 7, so that at least one ignition jet 6 extends from the cover 7 into the combustion chamber 2. The ignition jet 6 consists of a burning fuel-air mixture, through which ignition is caused, i.e., the fuel-air mixture starts to burn in the combustion chamber 2.

[0014] exist Figure 1 , a pre-chamber spark plug with three ignition beams is shown. However, any other number of ignition beams can also be envisaged. There is a time delay between the ignition spark in the interior of the cover 7 and at least one ignition beam. This time delay must be taken into account accordingly when operating the pre-chamber spark plug 3. Then, the combustion of the fuel-air mixture in the combustion chamber 2 is triggered by the at least one ignition beam 6. Here, this combustion is triggered simultaneously at multiple locations in the combustion chamber 2, rather than being triggered in a point-like manner as in the hook-shaped spark plug. This combustion triggered at multiple locations in the combustion chamber 2 improves the conversion of combustion energy into mechanical power, that is, the combustion is more efficient than in the case of local triggering of combustion by the hook-shaped spark plug. Therefore, by using the pre-chamber spark plug, a favorable operation of the internal combustion engine 1 can be achieved. It is therefore advantageous that the combustion in the combustion chamber 2 is preferably triggered by the pre-chamber spark plug 3. In addition, this combustion triggered simultaneously at multiple locations in the combustion chamber is significantly more effective for anti-knock combustion. If knocking occurs, the common practice can also be used in the case of pre-chamber spark plugs to reduce the knock frequency. In particular, the time of the combustion initiation can be correspondingly shifted to a later time in order to avoid the occurrence of knocking.

[0015] Figure 1 An internal combustion engine 1 is shown with two spark plugs, namely a hook spark plug 4 and a pre-chamber spark plug 3. Depending on the operating range of the internal combustion engine 1, the two spark plugs can be used differently. Figure 2 The operating range of an internal combustion engine is schematically shown in FIG.

[0016] exist Figure 2 1 shows the operating range of the internal combustion engine 1 with respect to its operating parameters "speed (n)" and "load (L)". The operation of the internal combustion engine 1 is limited in terms of speed so that the operation of the internal combustion engine cannot be carried out below speed n0 and above speed n1.

[0017] In terms of load, the curve 21 shown shows the full load curve. Depending on the speed, this full load curve 21 represents the respective maximum possible load state of the internal combustion engine.

[0018] In addition, a knock curve 22 is shown. The operating region between the full load curve 21 and the knock curve 22 is a knock-prone operating region, in which knock may occur depending on other operating parameters of the internal combustion engine 1. The determination of this knock curve 22 is a design issue, which depends on the permissible percentage of knock combustion (knock events). If, for example, a knock event occurs once every 100,000 combustions or a knock event occurs once every 1,000,000 combustions as a standard, the knock curve 22 is shifted accordingly. In this knock-prone operating region, the combustion is triggered by the ignition jet 6 of the pre-chamber spark plug 4, because this enables particularly efficient operation of the internal combustion engine 1. In addition, by triggering the combustion by the pre-chamber spark plug 4, the knock tendency is usually reduced, which is also advantageous in this operating region. If knock occurs, the knock tendency can be further reduced by the time delay of the ignition jet 6. In addition to the initiation of combustion by the ignition jet 6, an ignition spark can also be triggered at the hook spark plug 4. However, this is done with a small time delay in order to ensure the ignition by the pre-chamber spark plug 3. The time delay between the ignition in the chamber 7 of the pre-chamber spark plug 3 and the emergence of the ignition jet 6 must be taken into account accordingly. The additional ignition sparks at the hook spark plug prevent soot particles from being deposited on the hook spark plugs 3. In addition, combustion that usually takes place from multiple ignition sources is beneficial, so that a further small improvement in the combustion can be achieved by the additional ignition sparks at the hook spark plug 3.

[0019] exist Figure 2, a further curve of the ignition curve 23 is shown, which delimits the region in which reliable ignition cannot be ensured by the pre-chamber spark plug 4. In particular, under low load conditions, the amount of fuel injected is so small that there is no fuel-air mixture in the chamber 7 of the pre-chamber spark plug 4 that is sufficient for ignition, or the filling amount in the pre-chamber spark plug is so low that the generated ignition jet is too small to ignite the main combustion chamber. Therefore, in the load range below the ignition curve 23, too many combustion processes are not triggered only by the pre-chamber spark plug 4, but misfires occur. The exact definition of this ignition curve 23 is a design issue, which depends on the permissible percentage of unsuccessful combustion (misfires) caused by the triggering of the pre-chamber spark plug 4. If, for example, a misfire occurs once in 1,000 combustions or once in 100,000 combustions as a standard, the curve 23 is shifted accordingly. Therefore, in the operating range below the ignition curve 23, operation is carried out using the hook spark plug 3, i.e. the combustion is triggered by the hook spark plug 3. In addition, however, an ignition jet 6 of the pre-chamber spark plug 3 can also be carried out in order to reduce the deposition of soot on the pre-chamber spark plug 3 or to improve the combustion quality. Here, this additional ignition jet 6 should have a small time delay with respect to the triggering of the combustion by the ignition spark, so that the actual definition of the start of combustion is achieved by the hook spark plug 3. Here too, the time delay between the ignition time point in the pre-chamber spark plug and the outflow of the ignition jet must be taken into account.

[0020] In the operating region between the knock curve 22 and the ignition curve 23, combustion can be triggered both by the hook spark plug 3 and by the pre-chamber spark plug 4. However, since triggering the combustion by the pre-chamber spark plug 4 generally achieves more efficient combustion, for this operating region, triggering the combustion by the pre-chamber spark plug 4 is also preferred. However, depending on other operating parameters of the internal combustion engine, a more differentiated operating strategy can also be set for this region.

[0021] By heating the exhaust system of the internal combustion engine 1, a further operating range is defined. This operation for heating the exhaust system preferably uses very late ignition angles. These late ignition angles increase the temperature of the exhaust gases and enable efficient heating of the exhaust system. In this operation, ignition by means of a hook spark plug 3 is advantageous, since a later initiation of the combustion can be achieved with the ignition spark than with an ignition jet by means of a pre-chamber spark plug. Furthermore, this operating range is intentionally inactive in order to achieve a stronger heating of the exhaust system. Therefore, in this operation for heating, the initiation of the combustion is performed by means of the hook spark plug 3.

[0022] The optimal ignition time is determined by triggering the hook spark plug. The ignition time of the pre-chamber spark plug is provided with an offset, which is selected in such a way that the running smoothness of the internal combustion engine is improved. The ignition time of the hook spark plug and the offset for the pre-chamber spark plug are set as a function of the engine parameters (speed, load, charge, temperature, etc.). For reasons of carbon deposits, the pre-chamber spark plug is preferably always "followed" by the ignition, even if no advantages are obtained in terms of combustion stability, which can be checked and set specifically for each engine.

[0023] Another special operating state of the internal combustion engine 1 is the starting of the internal combustion engine 1. During the start, the combustion is triggered simultaneously by the ignition jet 6 and the ignition spark. This should therefore ensure a safe start of the internal combustion engine. Only then are different operating strategies implemented, in which the ignition is selectively carried out by the hook spark plug 4 or by the pre-chamber spark plug 3.

Claims

1. A method for controlling an internal combustion engine (1) having a pre-chamber spark plug (3) and a further hook spark plug (4) in a combustion chamber (2), characterized in that: In a first operating range of the internal combustion engine (1), combustion in the combustion chamber (2) is triggered by the pre-chamber spark plug (3), and in a second operating range of the internal combustion engine, combustion is triggered by the hook spark plug (4).

2. The method according to claim 1, characterized in that The triggering of combustion by the hook spark plug (4) is achieved by an ignition spark, and the triggering of combustion by the pre-chamber spark plug (3) is achieved by at least one ignition jet (6) extending from the pre-chamber spark plug (3) into the combustion chamber (2).

3. The method according to any one of the preceding claims, characterized in that When operating in a first operating range in which the pre-combustion chamber spark plug is triggered, an ignition spark is achieved on the hook spark plug (4) with a time delay after the ignition jet (6), and when operating in a second operating range in which combustion is triggered by the ignition spark on the hook spark plug (4), an ignition jet (6) is achieved into the combustion chamber (2) with a time delay after the ignition spark.

4. The method according to any one of the preceding claims, characterized in that The first operating range is characterized by a knock-prone operation of the internal combustion engine, in particular by a high load on the internal combustion engine.

5. The method according to claim 4, characterized in that When knock occurs, the time at which combustion is triggered by the pre-chamber spark plug is shifted toward a later combustion.

6. The method according to claims 1 to 3, characterized in that The first operating range is characterized in that combustion in the combustion chamber can be reliably initiated by the pre-chamber spark plug (3).

7. The method according to any one of the preceding claims, characterized in that The second operating range is characterized in that combustion in the combustion chamber (2) cannot be reliably initiated by the pre-chamber spark plug (3).

8. The method according to claim 7, characterized in that The second operating range is characterized by low load or by operation for heating the exhaust gas system of the internal combustion engine (1).

9. A device for controlling an internal combustion engine (1) having a pre-chamber spark plug (3) and a hook spark plug (4) in a combustion chamber (2), characterized in that: The device triggers combustion in the combustion chamber in a first operating range of the internal combustion engine by means of the pre-chamber spark plug (3) and triggers combustion in a second operating range of the internal combustion engine by means of the hook spark plug (4).

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