Method for actively damping the starting resonance of a torsional damper when starting an internal combustion engine

Abstract

The present invention relates to a method for actively damping the starting resonance of a torsional damper when starting an internal combustion engine, wherein the torsional damper (4) is fixed between the internal combustion engine (1) and a torsionally elastic secondary (5), and the internal combustion engine (1) is started using a starting motor (3) located on the side of the internal combustion engine (1) opposite the torsionally elastic secondary. A simple method for damping the starting resonance of the torsion damper can be achieved by applying a counter excitation to the torque generated by the starting motor (3) when the internal combustion engine (1) is started, and modulating the counter excitation based on parameters of the internal combustion engine (1) that change as the internal combustion engine (1) is started.

Description

Technical Field

[0001] The present invention relates to a method for actively damping the starting resonance of a torsional damper when starting an internal combustion engine, wherein the torsional damper is fixed between the internal combustion engine and the secondary side of the torsional elasticity, and the internal combustion engine is started using a starting engine arranged on the side of the internal combustion engine opposite to the torsional elasticity.

Background Art

[0002] A method for operating a motor vehicle is known from EP1 497 151 B1, wherein the internal combustion engine is started by a starting engine, and a clutch for temporarily connecting the starting engine and the internal combustion engine is arranged between the starting engine and the internal combustion engine.

[0003] DE10 2015 207 640 A1 discloses a drive train and its operating method. The drive train comprises an internal combustion engine having a crankshaft. On the output side of the crankshaft, there is a dual-mass flywheel including a primary side and a secondary side that can be rotationally limited relative to the primary side contrary to the action of the spring device. The starting engine is arranged on the belt pulley surface of the internal combustion engine. In order to avoid an increase in the rotational angle between the primary and secondary disks of the dual-mass flywheel when the internal combustion engine is started, a starting machine is effectively arranged on the secondary side. This is intended to bypass the resonance range of the dual-mass flywheel when the internal combustion engine is started. Such an arrangement is very complex because, in addition to the starting engine, a further starting machine is required to drive the secondary side of the dual-mass flywheel.

Summary of the Invention

Problems to be Solved by the Invention

[0004] The object of the present invention is to provide a method for actively damping the starting resonance of a torsional damper when starting an internal combustion engine without requiring additional hardware.

Means for Solving the Problem

[0005] According to the present invention, this object is achieved when the internal combustion engine is started, by applying counter-excitation to the torque generated by the starting engine, and the counter-excitation is modulated based on parameters of the internal combustion engine that change when the internal combustion engine is started. Such a solution, which can be implemented only by software, reduces the influence of starting resonance on torsional elasticity. At the same time, both the resonance of the torsional damper and any rotational irregularities that the internal combustion engine performs due to the contraction and expansion torques during the starting process to set the crankshaft to operate are reduced. This has the advantage that low-friction torsional elasticity can also be used in the drive train.

[0006] The counter-excitation is advantageously modulated based on the crankshaft angle by means of n-th harmonic excitation of the internal combustion engine. The n-th harmonic excitation is superimposed on the torque of the starting engine. Such counter-excitation compensates for the resonant vibrations of the internal combustion engine and the torsional damper.

[0007] In one embodiment, the counter-excitation is set based on the speed of the internal combustion engine and / or the speed difference and / or the rotational angle difference between the internal combustion engine and the starting engine, or between the internal combustion engine and the transmission. The parameters used can be determined individually based on each drive train.

[0008] In a variant, the torque of the starting engine is superimposed with a counter-excitation designed as a sine function during the starting process of the internal combustion engine. This takes into account that the rotational irregularities caused by the internal combustion engine are periodic even without ignition excitation, and therefore can be compensated particularly well by the counter-excitation designed as a sine function.

[0009] In one embodiment, the nominal torque of the starting motor is exceeded during start-up such that a counter-excitation is superimposed on the torque of the starting motor. This can always be advantageously used when the electrical design of the starting motor allows it to operate overloaded for a short time.

[0010] In an alternative, the average torque of the starting motor is reduced during start-up such that a counter-excitation is superimposed on the torque of the starting motor. As a result, the start-up process is slowed down. However, by reducing the average torque of the starting motor, the counter-excitation can be correspondingly increased, whereby the rotational irregularity of the internal combustion engine can be compensated particularly well.

[0011] In a further alternative, the counter-excitation is reduced during start-up in the upper speed range of the internal combustion engine. In this speed range of the internal combustion engine, which is close to the idling speed, the internal combustion engine no longer generates such high rotational irregularities.

[0012] In a further embodiment, the phase position of the counter-excitation is shifted taking into account the stiffness of the belt drive arranged between the starting motor and the internal combustion engine. This enables the crankshaft angle to be achieved at the exact time by the counter-excitation, whereby sufficient compensation of the starting resonance is obtained.

[0013] The present invention enables a number of embodiments. One of these will be described in more detail with reference to the figures shown in the drawings.

Brief Description of the Drawings

[0014]

Figure 1

Figure 2

Figure 3

Figure 4

DETAILED DESCRIPTION OF THE INVENTION

[0015] FIG. 1 shows a basic diagram of an internal combustion engine in a drive train, where the internal combustion engine 1 is connected to a starting engine 3 via a belt drive 2. On the opposite side of the internal combustion engine 1, a torsional damper 4 is connected, which is then, in turn, connected to the secondary side 5 of a dual mass flywheel. The dual mass flywheel is an example of torsional elasticity.

[0016] FIG. 2 shows an exemplary embodiment of the method according to the invention, showing that the internal combustion engine 1 is started by the starting engine 3. Column A shows the operation of the system without superimposing reverse excitation on the torque of the starting engine 3, and column B shows the behavior of the system with reverse excitation superimposed on the torque of the starting engine 3. In row a, the torque M is shown based on the time t. Row b shows the speed n with respect to the time t, and row c shows the rotational angle φ of the dual mass flywheel. In all of these figures, curve I characterizes the behavior of the starter, curve II characterizes the behavior of the internal combustion engine 1, and curve III characterizes the behavior of the secondary side 5 of the dual mass flywheel.

[0017] In section Aa, it can be seen that the starting engine 3 initially expends high torque to start the internal combustion engine 1, and the torque weakens over time. The internal combustion engine 1 restarts with zero torque until the torque of the starting engine 3 becomes effective and ignition of the internal combustion engine 1, shown as a peak, is achieved. From section Ba, it can be seen that the torque of the starting engine 3 is much more non-uniform due to the superposition of counter-excitation, and the maximum value of the torque of the internal combustion engine 1 and the modulated torque of the starting engine 3, and / or the minimum value of the torque of the internal combustion engine 1 and the starting engine 3 are always close to each other. In the current case, the torque of the starting engine 3 during the start-up of the internal combustion engine 1 is superimposed with a sine function that depends on the respective engine order, preferably the crankshaft angle in the first harmonic of the main excitation of the internal combustion engine 1. As a result, the speed of the starting engine 3 is increased over time t (Figure Bb) in order to reduce the speeds of the internal combustion engine 3 and the secondary side 5 of the dual-mass flywheel. As an effect, as shown in section Bc, the rotational angle φ of the secondary side 5 of the dual-mass flywheel is reduced compared to the method without counter-excitation (section Ac). The resonance R is significantly reduced with the help of the solution according to the invention.

[0018] There are various ways in which the starting engine 3 can be controlled during the superposition by counter-excitation. Therefore, the starting engine 3 can exceed its nominal torque in some areas, and the starting engine 3 operates overloaded for a short time.

[0019] In an alternative example, as shown in Figure 4, the average torque of the starting engine 3 is reduced. The torque curve that actively damps the starting resonance of the torsional damper 4 is shown against time t, and the torque curve corresponds to amplitude * sin(2 × crankshaft angle + phase).

[0020] Another possibility enables starting processes to be carried out in the upper speed range of an internal combustion engine where the amplitude of the reverse excitation is reduced. This can be achieved because less reverse excitation is required in such a high-frequency range of the starting resonance. When the internal combustion engine 1 rotates slowly, the torque and the reverse excitation have a lower frequency, and when the internal combustion engine 1 rotates faster, they should always be presumed to increase.

[0021] To optimize the effectiveness of the reverse excitation, the phase position and / or the amplitude of the superimposed sine function are shifted, which means that the stiffness of the belt drive 2 is also taken into account. This ensures that the maximum or minimum value of the modulated torque of the starting engine 3 is applied to the crankshaft of the internal combustion engine 1 at the exact time. Setting the reverse excitation based on the crankshaft angle is the simplest way to actively damp the starting resonance of the torsional damper 4. However, setting based on the speed, the speed difference or the rotational angle difference between the internal combustion engine and the engine or between the internal combustion engine and the transmission is also conceivable.

Explanation of symbols

[0022] 1 Internal combustion engine 2 Belt drive 3 Starting engine 4 Torsional damper 5 Secondary side of the dual-mass flywheel

Claims

1. A method for actively damping the starting resonance of a torsional damper when starting an internal combustion engine, wherein the torsional damper (4) is fixed between the internal combustion engine (1) and the secondary side (5) of a dual mass flywheel, and the internal combustion engine (1) is started using a starting engine (3) arranged on the side opposite to the side where the secondary side (5) of the dual mass flywheel is formed in the internal combustion engine (1). In this method, the internal combustion engine (1) is connected to the starting engine (3) via a belt drive (2). When the internal combustion engine (1) is started, counter excitation is applied to the torque generated by the starting engine (3). The counter excitation is set based on the speed of the internal combustion engine (1) that changes when the internal combustion engine (1) is started so that the rigidity of the belt drive (2) is taken into account and / or the speed difference and / or the rotational angle difference between the internal combustion engine (1) and the starting engine (3) or between the internal combustion engine (1) and the transmission. The method is characterized in that the phase position of the counter excitation is shifted to optimize so that the maximum value of the torque of the internal combustion engine (1) and the torque of the starting engine (3) to which the set counter excitation is applied are close to each other, and the minimum value of the torque of the internal combustion engine (1) and the torque of the starting engine (3) to which the set counter excitation is applied are close to each other.

2. The method according to claim 1, characterized in that the torque of the starting engine (3) is superimposed with a counter excitation designed as a sine function during the starting process of the internal combustion engine (1).

3. The method according to claim 1 or 2, characterized in that the rated torque of the starting engine (3) is exceeded during the starting process to superimpose the counter excitation on the torque of the starting engine (3).

4. The method according to claim 1 or 2, characterized in that the average torque of the starting engine (3) is reduced during the starting process to superimpose the counter excitation on the torque of the starting engine (3).

5. The method according to claim 1 or 2, characterized in that the counter excitation is reduced during the starting process in a speed range close to the idling speed of the internal combustion engine (1).

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