Method for increasing the reproducibility of the start-up during start-stop operation of an internal combustion engine

1. A method for providing a smooth start-up in a start-stop operation of an internal combustion engine, comprising:

detecting a crankshaft angular stop position (α Stopp ) of the internal combustion engine;

determining a speed gradient corresponding with an initial combustion of a start optimization operation of the internal combustion engine subject to the stop position (α stopp ) with a volume of fuel and a volume of air present in a cylinder of the internal combustion engine at an predetermined ignition angle; and

reducing the speed gradient to a predetermined speed gradient for different stop positions (α stopp ) by retarding an ignition angle or by retarding an inlet valve timing to reduce the cylinder charge for the initial combustion.

2. The method according to claim 1 , wherein the speed gradient corresponding with an initial combustion of a start optimization is a maximum speed gradient (ω max ).

3. The method according to claim 2 , further comprising:

determining an engine characteristic map for the maximum speed gradient (ω max ) that displays the maximum speed gradient (ω max ) as a function of an optimal ignition angle, an optimal volume of fuel subject to the stop position (α Stopp ), and an engine temperature (TCO) of the internal combustion engine.

4. The method according to claim 3 , wherein the set speed gradient is defined by the maximum speed gradient ω max at a set reference stop position (α Stopp-Soll ) of the internal combustion engine.

5. The method according to claim 4 , further comprising:

determining the ignition retard angle for stop positions (α Stopp ≦α Stopp-Soll ) from an ignition angle efficiency (η IGA ), where the ignition angle efficiency is a function of the predetermined speed gradient, the reference stop position (α stopp-soll ), a reference engine temperature (TCO Soll ), the maximum speed gradient (ω max ), the stop position (α Stopp ) and the engine temperature (TCO) according to the formula:

η

IGA

⁡

(

α

Stopp

,

TCO

)

=

ω

max

⁡

(

α

Stopp

-

Soll

,

TCO

Soll

)

ω

max

⁡

(

α

Stopp

,

TCO

)

.

6. The method according to claim 4 further comprising:

reducing a cylinder charge for the initial combustion via retarding the inlet valve timing in order to reduce the maximum speed gradient.

7. The method according to claim 6 , wherein for the inlet valve timing retard, the stop position (α Stopp ) is determined by a close position of the inlet valve (EVS) where the stop position equals the close position (α Stopp =EVS).

8. The method according to claim 7 , further comprising:

determining the ignition angle retard using the inlet valve timing retard for the stop position α Stopp ≦α Stopp-Soll and the close position EVS≦α Stopp-Soll from an ignition angle efficiency (η IGA ) which is a function of the predetermined speed gradient and the maximum speed gradient (ω max ) according to the formula:

η

IGA

⁡

(

α

Stopp

,

TCO

)

=

ω

max

⁡

(

α

Stopp

-

Soll

,

TCO

Soll

)

ω

max

⁡

(

α

Stopp

=

EVS

,

TCO

)

.

9. The method according to claim 5 , further comprising:

determining the ignition angle retard for the initial combustion via an ignition angle offset (Δ IGA ) using the function α IGA =Δ IGA (η IGA , α Stopp , TCO) and retarding the optimal ignition angle of the initial combustion by the ignition angle offset.

10. The method according to claim 8 , further comprising:

determining the ignition angle retard for the initial combustion via an ignition angle offset (Δ IGA ) using the function Δ IGA =Δ IGA (η IGA , α Stopp , TCO) and retarding the optimal ignition angle of the initial combustion by the ignition angle offset.

11. A smooth start-up start-stop operation internal combustion control device, comprising:

a crankshaft angular stop position sensor that detects a crankshaft angular stop position of the internal combustion engine;

a fuel volume sensor and an air volume sensor that determine a fuel volume and an air volume present in a cylinder of the internal combustion engine;

an ignition angle sensor that determines an ignition angle of the internal combustion engine;

an inlet valve adjusting device; and

a control unit that:

determines a speed gradient corresponding with an initial combustion of a start optimization operation of the internal combustion engine that is subject to a stop position with the volume of fuel and air present in a cylinder of the internal combustion engine at an optimal ignition angle, and

reduces the speed gradient to a predetermined speed gradient for different stop positions by retarding an ignition angle or by retarding an inlet valve timing to specifically reduce the cylinder charge for the initial combustion to provide smooth start-up during start-stop operation of the internal combustion engine.

12. The device according to claim 11 , wherein the control device further comprises:

determining the ignition retard angle for stop positions from an ignition angle efficiency (η IGA ), where the ignition angle efficiency is a function of the predetermined speed gradient, the reference stop position (α stopp-soll ), a reference engine temperature (TCO Soll ), the maximum speed gradient (ω max ), the stop position (α Stopp ) and the engine temperature (TCO) according to the formula:

η

IGA

⁡

(

α

Stopp

,

TCO

)

=

ω

max

⁡

(

α

Stopp

-

Soll

,

TCO

Soll

)

ω

max

⁡

(

α

Stopp

,

TCO

)

.

13. The device according to claim 11 , wherein the control device further comprises:

determining the ignition angle retard using the inlet valve timing retard for the stop position α Stopp ≦α Stopp-Soll and the close position EVS≦α Stopp-Soll from an ignition angle efficiency (η IGA ) which is a function of the predetermined speed gradient and the maximum speed gradient (ω max ) according to the formula:

η

IGA

⁡

(

α

Stopp

,

TCO

)

=

ω

max

⁡

(

α

Stopp

-

Soll

,

TCO

Soll

)

ω

max

⁡

(

α

Stopp

=

EVS

,

TCO

)

.