Method for operating an internal combustion engine

• US 20090178648A1
• Filed: 01/05/2009
• Published: 07/16/2009
• Est. Priority Date: 01/11/2008
• Status: Active Grant

• Current Assignee: Andreas STIHL AG & Company KG (Stihl Holding AG & Company KG)
• Original Assignee: Andreas STIHL AG & Company KG (Stihl Holding AG & Company KG)
• Inventors: Dangelmaier, Manuel, Gegg, Tim, Neubauer, Andreas, Layher, Wolfgang
• Granted Patent: US 8,322,326 B2
• Time in Patent Office: Days
• US Class Current: 123/406.450
• CPC Class Codes: F02D 31/009 for maximum speed control
• CPC Class Codes: F02D 37/02 one of the functions being ignition
• CPC Class Codes: F02D 41/0097 using means for generating speed signals
• CPC Class Codes: F02D 41/3058 the engine working with a variable number of cycles
• CPC Class Codes: F02P 5/045 combined with electronic control of other engine functions, e.g. fuel injection in general F02D37/02
• CPC Class Codes: F02P 9/005 by weakening or suppression of sparks to limit the engine speed

Abstract

An internal combustion engine (8) has an ignition device, a device for supplying fuel and a device for detecting the rpm of the engine (8). The engine (8) includes a permissible limit rpm (n_g) and a control range (A) of the rpm (n) above the limit rpm (n_g). A method for operating the engine (8) provides that the rpm of the engine (8) is limited in the control range (A) because of suppression of the ignition in individual engine cycles wherein the rpm (n) lies above a control rpm (n_a) lying in the control range (A). In the control range, and to improve the exhaust-gas values, the noncombustion engine cycle ratio (NECR) is adjusted. The NECR indicates the ratio of the number of engine cycles wherein the ignition is suppressed to the total number of ignitions.

Claims

1. A method for operating an internal combustion engine assembly including an internal combustion engine, an ignition system for controlling the ignition in said engine, a device for supplying fuel and a detecting unit for detecting the engine rpm (n) of said internal combustion engine;

said engine defining a permissible limit engine rpm (n_g) and a control range (A) of said engine rpm (n) above said limit engine rpm (n_g);

the method comprising the steps of;

limiting said engine rpm (n) in said control range (A) by suppressing said ignition;

limiting the ignition in said control range (A) by suppressing the ignition in individual engine cycles wherein said engine rpm (n) lies above a control engine rpm (n_a);

forming a noncombustion engine cycle ratio (NECR) as the ratio of a number of engine cycles wherein the ignition is suppressed to the total number of the ignitions; and

,

shifting said noncombustion engine cycle ratio (NECR) in said control range (A).

2. The method of claim 1, wherein said noncombustion engine cycle ratio (NECR) is shifted by changing the supplied fuel quantity.

3. The method of claim 2, wherein said supplied fuel quantity is changed continuously.

4. The method of claim 3, wherein said supplied fuel quantity is reduced to shift said noncombustion engine cycle ratio (NECR).

5. The method of claim 1, wherein said noncombustion engine cycle ratio (NECR) is shifted until said noncombustion engine cycle ratio (NECR) has dropped to below 20%.

6. The method of claim 5, wherein said noncombustion engine cycle ratio (NECR) is shifted until said noncombustion engine cycle ratio (NECR) has dropped to below 10%.

7. The method of claim 6, wherein said noncombustion engine cycle ratio (NECR) is shifted until said noncombustion engine cycle ratio (NECR) has dropped to approximately 0%.

8. The method of claim 5, wherein a control variable for said engine is determined from parameters in said control range (A).

9. The method of claim 8, wherein a maximum (NECR_max) of said noncombustion engine cycle ratio (NECR) is determined in said control range (A).

10. The method of claim 9, wherein the method comprises the further steps of:

forming a characteristic line indicating a fuel quantity (x), which is to be supplied, as a function of said engine rpm (n); and

,

using said maximum (NECR_max) or a percentage part thereof for adjusting said characteristic line.

11. The method of claim 1, wherein the method comprises the further steps of:

forming a characteristic line indicating a fuel quantity (x), which is to be supplied, as a function of engine rpm (n);

for adjusting said characteristic line below said limit engine rpm (n_g), changing the air/fuel ratio and evaluating a change in said engine rpm (n) resulting from the changed air/fuel ratio.

12. The method of claim 11, wherein said air/fuel ratio is changed by changing the supplied fuel quantity.

13. The method of claim 1, wherein said device for supplying fuel meters the fuel quantity (x) which is to be supplied for each engine cycle.

14. The method of claim 1, wherein said method comprises the further steps of:

in said control range (A), monitoring a pattern (P) of engine cycles for which no ignition takes place; and

,

suppressing the ignition in the following engine cycle when said pattern (P) is coincident with a critical pattern (P_crit) of said engine cycles for which no ignition results.