Method and device for reducing the particulate emissions of an internal combustion engine, as well as a motor vehicle

Abstract

Method for controlling an internal combustion engine, comprising the following steps: - Supplying fuel to a combustion chamber of the internal combustion engine; - Ignition of the fuel in the combustion chamber; and - Detect that the internal combustion engine should deliver a higher actual power output (14; 24); - Shifting the ignition timing to a later time (34) compared to the ignition timing (32, 36) at a static power demand (12, 16) when it is detected that the internal combustion engine is to deliver a higher actual power; characterized in that the step of shifting the ignition timing to a later time (34) compared to the ignition timing at a static power demand (32, 36) is only carried out at a predetermined speed.

Description

[0001] The present invention relates to a method and a control device for reducing the particle emission of an internal combustion engine.

[0002] The operating principle of an internal combustion engine is well understood by experts. Fuel and air are supplied to the combustion chamber of the engine through valves. Once the combustion chamber valves are closed and a piston is in the appropriate position, i.e., near top dead center, the fuel-air mixture in the combustion chamber is ignited. Depending on the load, the amount of fuel supplied to the combustion chamber and the ignition timing vary.

[0003] Under dynamic load or during acceleration, a combustion engine emits more particles compared to a static load. The EU6c standard, expected to come into force in 2017, mandates stricter limits for particulate emissions from gasoline engines. These limits can only be met by certain vehicles through costly additional measures that significantly increase the vehicle's price.

[0004] The patent documents DE 10 2005 058 864 A1, DE 10 2013 204 901 A1, DE 10 2011 111 226 A1 and DE 198 06 665 A1 each describe operating methods for internal combustion engines and motor vehicles, respectively.

[0005] The invention therefore aims to create a method and a control device with which particle emissions are reduced.

[0006] The object of the invention is achieved by a method according to claim 1, a control device according to claim 6, and a motor vehicle according to claim 10. The dependent claims describe preferred embodiments.

[0007] The method can be further developed as described with regard to the device. The device can be further developed as described with regard to the method.

[0008] A method for controlling an internal combustion engine comprises the steps of supplying fuel to a combustion chamber of the engine, igniting the fuel in the combustion chamber, and detecting that the engine is required to deliver a higher actual power output. According to the invention, the ignition timing is retarded compared to the ignition timing under a static power demand when it is detected that the engine is required to deliver a higher actual power output. When the engine is required to deliver a higher actual power output, it exhibits positive load dynamics and / or positive speed dynamics. During acceleration of the vehicle, more particles are produced than under a static power demand.The inventor of the present invention has recognized that by shifting the ignition timing to a later point in time compared to the ignition timing at a static power demand, particulate emissions can be reduced. The torque reduction resulting from shifting the ignition timing to a later point in time is compensated for by a compensating torque.

[0009] The process further includes increasing the fuel supply to a combustion chamber of the internal combustion engine while simultaneously retarding the ignition timing compared to the ignition timing under static power demand. This increases the vehicle's fuel consumption. However, this is acceptable because acceleration phases are relatively short under normal operating conditions. The increased fuel supply adjusts the compensation torque. It is understood that the cylinder filling, or air supply, is increased proportionally with the fuel supply. Particulate reduction can be approximately 25%, depending on the driving cycle. The increase in fuel consumption can range from about 0.5% to 0.8%, again depending on the driving cycle.

[0010] By retarding the ignition timing or adjusting the ignition angle, the smoothness of the combustion engine is impaired. This can be tolerated, as a driver or passenger will not notice the reduced smoothness during acceleration.

[0011] The procedure can increase the torque reserve if it detects that the combustion engine is expected to deliver a higher actual power output and is therefore operating in a positive load and / or speed dynamic range. This is typically achieved by retarding the ignition timing to a later point that is optimal for the corresponding load case with regard to fuel consumption and / or smooth running, and by supplying more fuel to the combustion chamber and more air to the combustion engine.

[0012] Once the combustion engine has returned to a static operating state, the ignition timing can be gradually adjusted back to the optimal point for a static power demand. The ignition timing can be advanced via a ramp from the retarded point to the optimal point for a static power demand. The compensating torque, or torque reserve, is reduced accordingly. This reduces the number of particles emitted by the combustion engine during acceleration.

[0013] The step of retarding the ignition timing compared to the ignition timing under a static power demand is only performed below a predetermined maximum engine speed. According to one interpretation, the step of increasing the fuel supply to the combustion chamber of the internal combustion engine, compared to the fuel supply under a static power demand, is only performed below a predetermined maximum engine speed. By retarding the ignition timing compared to the optimal timing under a dynamic power demand, the engine's power output is reduced. Above a predetermined engine speed, the internal combustion engine must deliver maximum power or nearly maximum power.Therefore, in the range of maximum engine speed, it is not possible to postpone the ignition timing to a later point than the point optimal for maximum power output without impairing the power output of the internal combustion engine.

[0014] The process of retarding the ignition timing compared to the ignition timing at a static power demand, and / or increasing the fuel supply to the combustion chamber of the internal combustion engine compared to the fuel supply at a static power demand, is only performed under a predetermined load. Within the range of the internal combustion engine's maximum power output, it is not possible to retarder the ignition timing from the optimal point for power output to a later point.

[0015] The object of the invention is also achieved by a control device configured to control the fuel supply to an internal combustion engine and the ignition timing of the internal combustion engine, wherein the control device is configured to shift the ignition timing to a later time compared to the ignition timing at a static power demand when it is detected that the internal combustion engine is to deliver a higher actual power output. This reduces the number of particles emitted by the internal combustion engine.

[0016] The control device can be configured to increase the fuel and air supply to a combustion chamber of the internal combustion engine during the retarding of the ignition timing compared to the ignition timing under a static load demand. This compensates for the power reduction that results from retarding the ignition timing to a later point than the point that is optimal with regard to the power output of the internal combustion engine.

[0017] The control device is designed such that the retarding of the ignition timing compared to the ignition timing under a static power demand, and / or, according to one embodiment, the increasing of the fuel supply to the combustion chamber of the internal combustion engine compared to the fuel supply under a static power demand, is only carried out below a predetermined maximum engine speed. Furthermore, the control device can be designed such that the retarding of the ignition timing compared to the ignition timing under a static power demand, and / or the increasing of the fuel supply to the combustion chamber of the internal combustion engine compared to the fuel supply under a static power demand, is only carried out below a predetermined power demand.In the range of maximum engine speed and / or maximum power demand, the ignition timing or ignition angle cannot be shifted to a later time than the time that is optimal with regard to power output without impairing the power output of the internal combustion engine.

[0018] The invention also includes a motor vehicle with the control device described above.

[0019] The invention will now be described in more detail with reference to a non-restrictive embodiment, wherein Fig. 1 shows the target power output of an internal combustion engine; Fig. 2 shows the actual power output of an internal combustion engine; Fig. 3 shows the ignition timing or ignition angle; and Fig. 4 shows the fuel supply to a combustion chamber of the internal combustion engine.

[0020] The invention will now be explained using the example of an internal combustion engine installed in a motor vehicle. The operating principle of an internal combustion engine is known to those skilled in the art. A combustion chamber of an internal combustion engine, particularly a gasoline engine, comprises a cylindrical combustion chamber in which a piston attached to a crankshaft moves. The cylindrical combustion chamber is filled with air by means of a valve. In modern engines, the fuel is usually injected by means of injectors. Ignition is effected by means of a high voltage applied to a spark plug. The exhaust gas is directed out of the combustion chamber by means of an exhaust valve. A prior art internal combustion engine can have several combustion chambers and cylinders. Usually, the fuel-air mixture is ignited before the piston reaches top dead center. Fig. Figure 1 shows a target torque or power output that a driver of a motor vehicle can request from the internal combustion engine using the accelerator pedal or gas pedal, respectively. The abscissa represents time. The ordinate represents the torque or power that the internal combustion engine is intended to deliver.

[0021] Fig. Figure 2 shows the actual torque or power output of the internal combustion engine, with time represented on the abscissa and the actual torque or power output of the internal combustion engine shown on the ordinate.

[0022] Fig. Figure 3 shows the ignition point or ignition angle before reaching top dead center, with time plotted on the abscissa and the ignition point before top dead center shown on the ordinate.

[0023] Fig. Figure 4 shows the fuel supply to the at least one combustion chamber of the internal combustion engine, with the abscissa representing time and the ordinate representing the amount of fuel supplied to the at least one combustion chamber.

[0024] Fig. Figure 1 shows a first area 12 with a first target power requirement, and a first area with a static power requirement 12. This target power 12 is delivered by the combustion engine as actual power 22. Therefore, this power requirement is referred to as a static power requirement. Furthermore, Figure 1 shows... Fig. 1 and Fig. 2 a range with a dynamic power demand 14, 24 in which the internal combustion engine delivers less actual power than target power. This range is called the dynamic power demand and occurs, for example, during acceleration. Furthermore, show Fig. 1 and Fig. 2. A second area 16, 26 with a static power requirement, where the actual power and the target power of the internal combustion engine are equal. In areas with a static power requirement, the engine delivers the target power as actual power. With a dynamic power requirement, the engine delivers less actual power than the target power. This is the case, for example, when the engine is to accelerate the vehicle.

[0025] During the first static power demand (12, 22), the ignition timing or ignition angle is set to a first value 32 before reaching top dead center. During the second static power output (16, 26), the ignition timing or ignition angle is set to a second value 36 before reaching top dead center. The power output of the internal combustion engine is higher during the second static power output (16, 26) than during the first static power output (12, 22). Therefore, the ignition timing or ignition angle 36 is advanced further before top dead center during the second static power output (16, 26) than during the first power output (12, 22).

[0026] According to the invention, the ignition timing or ignition angle is shifted during the dynamic power demand 14 to a value 34 that may be closer to top dead center and / or after the ignition top dead center. The ignition timing or ignition angle is thus shifted to a later time 34 compared to the time that would be optimal for a static power demand and / or with regard to power output. This reduces the number of particles emitted by the internal combustion engine. As soon as the second static power demand 16, 26 is applied to the internal combustion engine, the ignition timing or ignition angle is shifted forward from the current value to the value 36 that is optimal for a static power demand, for example by means of a ramp 35.

[0027] Fig.Figure 4 shows the fuel supply to the at least one combustion chamber of the internal combustion engine. During the first static power demand range 12, 22, a first quantity of fuel 42 is supplied to the at least one combustion chamber. During the second static load demand range 16, 46, a second quantity of fuel 46 is supplied to the at least one combustion chamber of the internal combustion engine, the second quantity of fuel 46 being greater than the second quantity of fuel 42. During the dynamic power demand range 14, 24, a third quantity of fuel is supplied to the at least one combustion chamber of the internal combustion engine, the third quantity 44 being greater than the first quantity 42 and greater than the second quantity 46.As soon as the internal combustion engine has again reached the static power requirement 16, 26, the amount of fuel supplied to at least one combustion chamber of the internal combustion engine is reduced, for example by means of a ramp 45, to the extent that the ignition timing or ignition angle 35 is shifted to the optimal value 36.

[0028] It is understood that increasing the fuel supply also increases the air supply. The combustion engine can be controlled so that the fuel-air mixture remains constant when the fuel supply is increased. Alternatively, the combustion engine can be controlled so that the stoichiometric fuel-air ratio does not change when the fuel supply is increased. The present invention reduces the particles emitted by an internal combustion engine using simple measures. The slightly higher fuel consumption is acceptable in a typical driving cycle.

Claims

[1] Method for controlling an internal combustion engine, comprising the following steps: - Supplying fuel to a combustion chamber of the internal combustion engine; - Ignition of the fuel in the combustion chamber; and - Detect that the internal combustion engine should deliver a higher actual power output (14; 24); - Shifting the ignition timing to a later time (34) compared with the ignition timing (32, 36) under a static power demand (12, 16) when it is detected that the internal combustion engine is to deliver a higher actual power; characterized by , that the step of shifting the ignition timing to a later time (34) compared with the ignition timing under a static power demand (32, 36) is only carried out under a predetermined speed. [2] Method according to claim 1, characterized bythe step of increasing the fuel supply (44) to a combustion chamber of the internal combustion engine compared with the fuel supply at a static power demand (42, 46), while shifting the ignition timing to a later time (34) compared with the ignition timing (32, 36) at a static power demand. [3] Method according to claim 1, characterized by Increasing a torque reserve if it is detected that the internal combustion engine is to deliver a higher actual power output (14). [4] Method according to claim 2, characterized by , that the step of increasing the fuel supply (44) to the combustion chamber of the internal combustion engine is carried out only at a predetermined speed compared to the fuel supply at a static power demand (42, 46). [5] Method according to one of claims 2 or 4, characterized by, that the step of shifting the ignition timing to a later time (34) compared with the ignition timing at a static power demand (32, 36) and / or the step of increasing the fuel supply (44) to the combustion chamber of the internal combustion engine compared with a static power demand (42, 46) are only carried out under a predetermined power demand. [6] Control device designed to control the fuel supply to an internal combustion engine and the ignition timing of the internal combustion engine, the control device designed to postpone the ignition timing to a later time (34) compared with the ignition timing at a static power demand (32, 36) when it is detected that the internal combustion engine is to deliver a higher actual power (14, 24), characterized by, that the shifting of the ignition timing to a later time (34) compared with the ignition timing under a static power demand (32, 36) is only carried out under a predetermined maximum speed. [7] Control device according to claim 6, characterized by , that the control device is designed to increase the fuel supply to a combustion chamber of the internal combustion engine during the shift of the ignition timing to a later time (34) compared with the ignition timing at a static power demand (32, 36) compared with the fuel supply at a static power demand (32, 36) (44). [8] Control device according to claim 7, characterized by, that the control device is designed so that the increase in the fuel supply (44) to the combustion chamber of the internal combustion engine, compared with the fuel supply (42, 46) at a static power demand (32, 36), is carried out only at a predetermined maximum speed. [9] Control device according to one of claims 7 or 8, characterized by , that the control device is designed so that the shifting of the ignition timing to a later time (34) compared with the ignition timing at a static power demand (32, 36) and / or the increase of the fuel supply (44) to the combustion chamber of the internal combustion engine compared with the fuel supply (42, 46) at a static power demand (32, 36) are only carried out under a predetermined power demand. [10] Motor vehicle with the control device according to one of claims 6 to 9.

Images