Method for operating a spark-ignited internal combustion engine

Abstract

Method for operating a spark-ignition internal combustion engine with at least one first combustion chamber and a second combustion chamber, wherein, for torque adjustment of the internal combustion engine, a first throttle element is provided for the first combustion chamber and a second throttle element for the second combustion chamber in a first and a second air intake channel, wherein each throttle element can be opened or closed separately for a combustion air flow rate, characterized by the following process steps at the torque required during braking of the internal combustion engine: - Closing the first throttle element, - Closing the second throttle element, - where the second throttle element is open up to 80% less than the first throttle element at its maximum opening angle. The operating method according to the invention achieves, for example, a higher torque resolution when torque is reduced both by driver request and by control interventions initiated by the control unit.

Description

[0001] The invention relates to a method for operating a spark-ignition internal combustion engine with the features from the preamble of claim 1.

[0002] In spark-ignition internal combustion engines, i.e., those operating on the Otto cycle, the required power output is regulated by the supplied air and fuel mass, which corresponds to quantitative mixture control. To regulate the air mass, a throttle valve is typically located in the intake tract between the air filter and the intake manifold, which distributes the air to the cylinders. Alternatively, as with BMW's fully variable valve train "Valvetronic," the air mass control can be implemented directly with the intake valves to minimize charge exchange losses. Another possibility, for example in racing engines such as those in a BMW M3, is to implement air mass control with individual throttle valves for each cylinder. The actuation of all individual throttle valves always occurs simultaneously, meaning at the same time for all cylinders.

[0003] An example of the use of individual throttle valves is described in German patent application DE 101 53 478 A1, from which the present invention is based. DE 101 53 478 A1 discloses a device for controlling a rotatable actuator, such as a throttle valve, in which the angular position of the actuator is adjustable. In this device, a constantly rotating shaft is located in the axis of rotation of the rotatable actuator, and the actuator can be coupled to the shaft via a drive coupling in a first function and to stationary components of the device via a locking coupling in a second function.

[0004] This embodiment makes it possible to replace the conventional common throttle valve at the intake manifold inlet with individual throttle valves directly upstream of the intake valves of the internal combustion engine cylinders, resulting in fuel savings and, furthermore, a simple method of cylinder deactivation to reduce fuel consumption and emissions. This device ensures that the throttle valve actuators are designed for rapid switching and that the high actuating and holding forces required by the high air velocities of the intake airflow can be achieved. Compared to purely individual actuators for each throttle valve, this design offers significant cost and weight advantages, and, depending on the specific coupling design, also advantageous reductions in installation space.

[0005] However, disadvantages of all known designs include, for example, poor torque resolution and a very slow response time of the internal combustion engines to torque change requests, for example by the driver or by an electronic control unit.

[0006] From US patent 2006 / 0048746A1, an internal combustion engine is known which has a plurality of cylinders divided into two or more groups, with at least some of the cylinders being stabilized. The throttle valve of each cylinder can be actuated independently of the group to which the cylinder belongs, and the number of inert cylinders is controlled according to the throttle grip opening. The throttle valve opening differs between the groups, except for the fully open and fully closed positions. A control unit is provided to open the throttle valve of the next cylinder group before the throttle valve of the first cylinder group reaches its fully open position.

[0007] The object of the present invention is to demonstrate a measure or at least a method by which the aforementioned disadvantages are avoided.

[0008] This problem is solved by the process steps in the characterizing parts of claim 1 during braking operation (reduction of the torque requirement).

[0009] The method according to the invention significantly improves the resolution of torque responses to changes in torque, whether initiated by the driver of the motor vehicle or by a control unit. This advantageously reduces the reaction time of either the driver or the control unit to the change in torque. The method according to the invention can be used in the operation of a spark-ignition internal combustion engine with at least two cylinders and, furthermore, with any number of cylinders. Thus, at least two to n throttle elements can be provided to restrict the air supply to the internal combustion engine. Advantageously, cylinder-specific control of the throttle elements or control in subgroups (e.g., cylinders) is possible.In a four-cylinder internal combustion engine, this involves the simultaneous control of the throttle elements of cylinders 1 and 3 and cylinders 2 and 4, or cylinders 1 and 2 and cylinders 3 and 4, which establish a specifically different airflow from cylinder to cylinder or from cylinder group to cylinder group. This can be an inline, V-configuration, boxer, or radial internal combustion engine. The method can also be used for single-track vehicles, such as motorcycles, or for two-track vehicles, such as passenger cars or trucks. The goal is always to achieve, for example, higher torque resolution when torque changes or decreases, either due to driver input or control interventions initiated by the engine control unit.

[0010] The invention is explained in more detail below with reference to three figures. Fig. Figure 1 shows in a first diagram different opening angles of a first and a second throttle element for a speed of 5000 rpm, when increasing the torque. Fig. Figure 2 shows in a second diagram the different opening angles of the first and second throttle elements at a speed of 10,000 rpm, when increasing the torque. Fig. Figure 3 shows in a third diagram the different opening angles of the first and second throttle elements at a speed of 15,000 rpm, when increasing the torque.

[0011] The following apply in the Fig. 1, Fig. 2 to Fig. 3 the same reference numbers.

[0012] The next three paragraphs also apply to the Fig. 1, Fig. 2 to Fig. 3 in common: In the Fig. 1 to Fig. Figure 3 shows three diagrams, each plotted on the Y-axis, representing an opening angle of a first and a second throttle element from 0 to 110 [%]. A maximum opening angle corresponds to 100 [%]. A target torque from -40 to 140 [Nm] is plotted on the X-axis.

[0013] A maximum achievable target torque at the respective rotational speed applicable to the diagram is indicated by a vertical dashed line numbered 3. A defined initial torque is represented by a thin, vertical solid line numbered 4. The opening angle of the first throttle element (Throttle 1) is indicated by a thin line numbered 1, and the opening angle of a second throttle element (Throttle 2) is indicated by a thick line numbered 2.

[0014] In the Fig. 1, Fig. 2 to Fig. Figure 3 shows the opening angle of the first and second throttle elements 1, 2 for increasing the torque at a constant engine speed. No figures are shown for the case of a decrease in torque (vehicle deceleration), as the same principle applies.

[0015] Fig. Figure 1 shows different opening angles of the first and second throttle elements 1, 2 at a speed of 5000 rpm when increasing the torque, according to a method for operating a spark-ignition internal combustion engine (not shown) with at least one first combustion chamber and one second combustion chamber. For torque adjustment of the internal combustion engine, the first throttle element 1 is provided for the first combustion chamber and the second throttle element 2 for the second combustion chamber in a first and a second air intake channel, respectively. Each throttle element 1, 2 can be opened or closed separately for a combustion air flow rate. The process steps for increasing the torque requested by the internal combustion engine to a target torque 3 are shown. ❖ Opening of the first throttle element 1 until a defined first torque 4 is reached, in this case at 5000 rpm of the internal combustion engine this is approximately 20 Nm, ❖ Opening the second throttle element 2, ❖ Further opening of the first and second throttle elements 1, 2 until the target torque 3 is reached.

[0016] Preferably, the second throttle element 2 is opened up to 80% less than the first throttle element 1 until the target torque 3 is reached.

[0017] When the target torque 3 is reached, the opening angles of the first throttle element 1 and the opening angle of the second throttle element 2 are equal and amount to in Fig. 1 approx. 43%.

[0018] The following procedure steps apply analogously when reducing the torque of the internal combustion engine: ❖ Closing of the first throttle element 1, ❖ Closing the second throttle element 2, ❖ where the second throttle element is open up to 80% less than the first throttle element at its maximum opening angle

[0019] The different opening or closing of the first and second throttle elements 1, 2 can be achieved as desired, for example by means of different Bowden cables, which are controlled manually or by electric actuators. Hydraulic actuation of the throttle elements 1, 2 is also conceivable.

[0020] For example, a throttle valve can be used as the throttling element 1, 2; roller slides and other closure elements are also possible.

[0021] The method according to the invention can advantageously be used in the operation of a spark-ignition internal combustion engine with at least two cylinders and, furthermore, with any number of cylinders. Thus, at least two to n throttle elements can be provided to throttle the air supply to the internal combustion engine. Advantageously, cylinder-specific control of the throttle elements or control in subgroups (e.g., in a four-cylinder internal combustion engine: simultaneous control of the throttle element of cylinders 1 and 3 and cylinders 2 and 4, or of cylinders 1 and 2 and cylinders 3 and 4), which establish a specifically different air flow rate from cylinder to cylinder or from cylinder group to cylinder group, is demonstrated. This can involve an inline internal combustion engine, a V-configuration engine, a boxer engine, or a radial engine.The method can also be used for single-track vehicles, such as motorcycles, or for two-track vehicles, such as passenger cars or trucks. The aim is always to achieve a higher torque resolution when the torque changes, both when increasing the torque according to claim 1 and when decreasing it according to claim 3, either through driver input or through control interventions initiated by the control unit.

[0022] Fig. 2 shows the same context as Fig. 1, however, for an engine speed of 10,000 rpm. The target torque 3 is approximately 125 Nm at 10,000 rpm, with the defined first torque being approximately 30 Nm. At maximum torque, the opening angle of the first throttle element 1 and the opening angle of the second throttle element 2 are each 100%.

[0023] Fig. Figure 3 again shows the same relationship as the Fig. 1 and Fig. 2, however, for an internal combustion engine speed of 15,000 rpm. The target torque 3 is approximately 105 Nm at 15,000 rpm, and the defined first torque 4 is approximately 8 Nm. Also at 15,000 rpm of the internal combustion engine, the opening angle of the first throttle element 1 and the opening angle of the second throttle element 2 are each 100% when the target torque 3 is reached. Reference symbol list: 1 Opening angle of first throttle element 2 Opening angle of second throttle element 3 Target torque 4 defined first torque

Claims

[1] Method for operating a spark-ignition internal combustion engine with at least a first combustion chamber and a second combustion chamber, wherein for torque control of the internal combustion engine a first throttle element is provided for the first combustion chamber and a second throttle element is provided for the second combustion chamber in a first and a second air intake channel, wherein each throttle element can be opened or closed separately for a combustion air flow rate, characterized by The following process steps are involved in the torque required during braking of the internal combustion engine: - Closing the first throttle element, - Closing the second throttle element, - where the second throttle element is open up to 80% less than the first throttle element at its maximum opening angle.

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