Method for starting an internal combustion engine with the aid of a belt-driven starter generator

1. A method for starting an internal combustion engine using a starter generator to which the internal combustion engine is connected via a belt drive, the belt drive including a belt pulley of the starter generator, a belt pulley of the internal combustion engine, and a belt connecting the belt pulleys in a torque-transmitting manner, the method comprising:

operating the starter generator such that its drive torque output M 0 to the belt pulley of the starter generator is according to a drive torque curve by which, taking a gear ratio i of the belt drive into consideration, an output torque M 1 generated temporarily on the belt pulley of the internal combustion engine exceeds the drive torque output M 0 of the starter generator, such that M 1 >M 0 *i; and

after the temporary exceedance, the output torque M 1 generated on the belt pulley of the internal combustion engine decaying over time from M 1 >M 0 *i to the drive torque output M 0 of the starter generator taking the gear ratio i into consideration, such that M 1 decays to M 0 *i, as the starter generator operates;

wherein the drive torque curve according to which the starter generator operates is a linear drive torque curve having a torque gradient of at least M max /(0.5*T 0 ), where M max is a peak torque value, and T 0 is a period duration of a first natural frequency of the belt drive;

wherein during the operating of the starter generator, a transmitted peak torque of the starter generator is less than a breakaway torque of a crankshaft of the internal combustion engine.

2. The method of claim 1 , wherein the temporary exceedance is by more than 40%.

3. The method of claim 1 , wherein the temporary exceedance is by more than 50%.

4. The method of claim 1 , wherein the operation of the starter generator is such that the drive torque output M 0 to the belt pulley of the starter generator increases from a torque of zero to a predefined setpoint drive torque value during a predefined acceleration duration.

5. The method of claim 4 , wherein the acceleration duration is predefined as a function of the period duration T 0 of the first natural frequency of the belt drive.

6. The method of claim 5 , wherein the acceleration duration is set to at most double the period duration T 0 of the first natural frequency of the belt drive.

7. The method of claim 5 , wherein the acceleration duration is set to be at most equal to the period duration T 0 of the first natural frequency of the belt drive.

8. The method of claim 5 , wherein the acceleration duration is set to half the period duration T 0 of the first natural frequency of the belt drive.

9. The method of claim 4 , wherein the acceleration duration is at least 0.5 μs.

10. The method of claim 1 , wherein the drive torque curve is predefined as a function of at least one variable, which is selected from the group consisting of a length of the belt span between the belt pulley of the starter generator and the belt pulley of the internal combustion engine, an axial rigidity of the belt, a moment of inertia of rotating elements of the starter generator and the belt pulley of the starter generator, and a radius of the belt pulley of the starter generator.

11. The method of claim 1 , wherein the decaying is a function of damping by the belt drive and the internal combustion engine.

12. The method as recited in claim 1 , wherein the drive torque output M 0 of the starter generator is a maximum peak torque output of the starter generator.

13. A device comprising:

processing circuitry; and

an interface to an engine-generator system that includes a starter generator to which an internal combustion engine is connected via a belt drive, the belt drive including (a) a belt pulley of the starter generator, (b) a belt pulley of the internal combustion engine, and (c) a belt connecting the belt pulleys in a torque-transmitting manner;

wherein the processing circuitry is configured to generate, and output to the engine-generator system, control output that operates the starter generator such that its drive torque output M 0 to the belt pulley of the starter generator is according to a drive torque curve by which, taking a gear ratio i of the belt drive into consideration, an output torque M 1 generated temporarily on the belt pulley of the internal combustion engine exceeds the drive torque output M 0 of the starter generator, such that M 1 >M 0 *i;

wherein after the temporary exceedance, the output torque M 1 generated on the belt pulley of the internal combustion engine decays over time from M 1 >M 0 *i to the drive torque output M 0 of the starter generator taking the gear ratio i into consideration, such that M 1 decays to M 0 *i, as the starter generator operates;

wherein the drive torque curve according to which the starter generator operates is a linear drive torque curve having a torque gradient of at least M max /(0.5*T 0 ), where M max is a peak torque value, and T 0 is a period duration of a first natural frequency of the belt drive;

wherein during the operating of the starter generator, a transmitted peak torque of the starter generator is less than a breakaway torque of a crankshaft of the internal combustion engine.

14. The device of claim 13 , wherein the decay is a function of damping by the belt drive and the internal combustion engine.

15. The device as recited in claim 13 , wherein the drive torque output M 0 of the starter generator is a maximum peak torque output of the starter generator.

16. A non-transitory computer-readable medium on which are stored instructions that are executable by a processor, the instructions which, when executed by the processor, cause the processor to perform a method for starting an internal combustion engine using a starter generator to which the internal combustion engine is connected via a belt drive, the belt drive including a belt pulley of the starter generator, a belt pulley of the internal combustion engine, and a belt connecting the belt pulleys in a torque-transmitting manner, the method comprising:

operating the starter generator such that its drive torque output M 0 to the belt pulley of the starter generator is according to a drive torque curve by which, taking a gear ratio i of the belt drive into consideration, an output torque M 1 generated temporarily on the belt pulley of the internal combustion engine exceeds the drive torque output M 0 of the starter generator, such that M 1 >M 0 *i; and

after the temporary exceedance, the output torque M 1 generated on the belt pulley of the internal combustion engine decaying over time from M 1 >M 0 *i to the drive torque output M 0 of the starter generator taking the gear ratio i into consideration, such that M 1 decays to M 0 *i, as the starter generator operates;

wherein the drive torque curve according to which the starter generator operates is a linear drive torque curve having a torque gradient of at least M max /(0.5*T 0 ), where M max is a peak torque value, and T 0 is a period duration of a first natural frequency of the belt drive;

wherein during the operating of the starter generator, a transmitted peak torque of the starter generator is less than a breakaway torque of a crankshaft of the internal combustion engine.

17. The non-transitory computer-readable medium of claim 16 , wherein the decaying is a function of damping by the belt drive and the internal combustion engine.

18. The non-transitory computer-readable medium of claim 16 , wherein the drive torque output M 0 of the starter generator is a maximum peak torque output of the starter generator.