Internal Combustion Engine and Method for Operating an Internal Combustion Engine

Abstract

An internal combustion engine has a cylinder with a combustion chamber delimited by a reciprocating piston that drives a crankshaft rotatably supported in a crankcase. The internal combustion engine has an intake passage, an exhaust connected to the combustion chamber, a device supplying fuel, and a control device controlling at least one operating parameter of the internal combustion engine. The internal combustion engine is operated in that a pressure is measured in operation of the internal combustion engine, an adjustable value for at least one operating parameter of the internal combustion engine is deteremined based on the measured pressure, and the determined adjustable value is set for optimized running of the engine.

Description

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is a schematic illustration of an internal combustion engine in longitudinal section.

FIG. 2 is a section along the section line II-II of FIG. 1.

FIG. 3 is a perspective, partially sectioned, illustration of an internal combustion engine.

FIG. 4 is a schematic section illustration of a first arrangement of the temperature sensor.

FIG. 5 is a schematic section illustration of a second arrangement of the temperature sensor.

FIG. 6 is a graph of the course of the pressure in the crankcase as a function of the crankshaft angle.

FIG. 7 is a graph of the course of the pressure in the crankcase as a function of the crankcase volume.

FIG. 8 is a flow chart of a first method for determining the air mass flow through the combustion chamber.

FIG. 9 is a flow chart of a second method for determining the air mass flow through the combustion chamber.

FIG. 10 is a flow chart of a third method for determining the air mass flow through the combustion chamber.

FIG. 11 is a diagram that illustrates the ignition timing as a function of the air mass flow and of the engine speed.

FIG. 12 is a schematic illustration of an internal combustion engine in longitudinal section.

FIG. 13 is a diagram illustrating the general sequence of steps of the method according to the invention.

Claims

1. A method for operating an internal combustion engine that comprises a cylinder with a combustion chamber, which combustion chamber is delimited by a reciprocating piston that drives a crankshaft rotatably supported in a crankcase, wherein the internal combustion engine further comprises an intake passage, an exhaust connected to the combustion chamber, a device supplying fuel, and a control device controlling at least one operating parameter of the internal combustion engine; the method comprising the steps of: a) measuring a pressure in operation of the internal combustion engine;b) determining an adjustable value for at least one operating parameter of the internal combustion engine based on the measured pressure of the step a);c) setting the determined adjustable value of step b).

2. The method according to claim 1, wherein in the step a) the pressure is measured in the crankcase.

3. The method according to claim 1, wherein in the step a) the pressure is measured as a relative pressure relative to a reference pressure.

4. The method according to claim 1, further comprising the step of measuring a temperature of the internal combustion engine.

5. The method according to claim 4, wherein the temperature is a component temperature.

6. The method according to claim 4, wherein the temperature is measured in the crankcase.

7. The method according to claim 6, wherein the temperature is an average crankcase temperature.

8. The method according to claim 6, wherein the pressure and the temperature are measured in the crankcase by a combined pressure/temperature sensor.

9. The method according to claim 1, wherein in the step a) the pressure is measured in the crankcase at a predetermined crankshaft angle.

10. The method according to claim 9, wherein at the predetermined crankshaft angle the crankcase is closed off.

11. The method according to claim 9, wherein, based on the pressure measured in the step a), an air quantity flowing through the combustion chamber is determined.

12. The method according to claim 11, further comprising the step of measuring the engine speed of the internal combustion engine.

13. The method according to claim 12, wherein the air quantity is determined with a characteristic map providing the air quantity as an air mass flow as a function of the engine speed and the pressure in the crankcase at the predetermined crankshaft angle.

14. The method according to claim 13, wherein the pressure is corrected based on a measured temperature and wherein the corrected pressure is used for determining the air mass flow in the characteristic map.

15. The method according to claim 12, wherein the air quantity is determined with a characteristic map providing the air quantity as an air mass flow as a function of the engine speed and a pressure difference between a first pressure measured at a first predetermined crankshaft angle and a second pressure measured at a second predetermined crankshaft angle.

16. The method according to claim 15, wherein the pressure difference is corrected based on a measured temperature and wherein the corrected pressure difference is used for determining the air mass flow in the characteristic map.

17. The method according to claim 11, wherein the air quantity flowing through the combustion chamber is calculated.

18. The method according to claim 17, wherein the pressure is measured at a first predetermined crankshaft angle during a compression phase of the crankcase and at a second predetermined crankshaft angle during an expansion phase of the crankcase.

19. The method according to claim 17, wherein the crankcase has a first volume at a first predetermined crankshaft angle and a second volume at a second predetermined crankshaft angle, wherein the first volume and the second volume are identical.

20. The method according to claim 17, wherein the crankcase has a first volume at a first predetermined crankshaft angle and a second volume at a second predetermined crankshaft angle, wherein the first volume is different from the second volume.

21. The method according to claim 17, wherein the internal combustion engine is a two-stroke engine having at least one transfer passage through which the combustion air sucked into the crankcase passes into the combustion chamber, wherein the air quantity is calculated as air mass flow m with equation m=Δm*A/60—with A being the number of working cycles per minute and m being the air mass flow per second—based on a calculation of a combustion air mass Δm transferred into the combustion chamber for one working cycle by employing the ideal-gas law, wherein the pressure and the temperature of the first predetermined crankshaft angle; the pressure and the temperature of the second predetermined crankshaft angle; volumes of the crankcase at the first and second predetermined crankshaft angles; and the gas constant are used in the ideal-gas law.

22. The method according to claim 21, wherein the temperature at the first predetermined crankshaft angle and the temperature at the second predetermined crankshaft angle are calculated based on a measured average crankcase temperature.

23. The method according to claim 22, wherein the temperature at the first predetermined crankshaft angle and the temperature at the second predetermined crankshaft angle are calculated based on a polytropic change of state and wherein a polytropic exponent for a state equation is determined with a characteristic map.

24. The method according to claim 21, wherein the air quantity is calculated based on a pressure difference of the pressure at the first predetermined crankshaft angle and of the pressure at the second predetermined crankshaft angle.

25. The method according to claim 1, wherein the operating parameter is a fuel quantity to be supplied for a working cycle of the internal combustion engine for achieving a predetermined lambda value in the combustion chamber.

26. The method according to claim 25, wherein the fuel quantity is supplied in a working cycle following a working cycle in which the pressure has been measured.

27. The method according to claim 25, wherein, when starting the internal combustion engine, a predetermined lambda value for a cold start or a predetermined lambda value for a hot start is selected based on the measured temperature and the fuel quantity matching the selected predetermined lambda value is determined.

28. The method according to claim 25, wherein the fuel quantity is supplied through a fuel valve and is controlled by controlling the timing of opening and closing of the fuel valve.

29. The method according to claim 1, wherein the operating parameter is an ignition timing of the internal combustion engine.

30. The method according to claim 29, wherein the ignition timing is determined with a characteristic map based on a measured engine speed and an air mass flow that has been determined.

31. An internal combustion engine comprising: a cylinder having a combustion chamber;a reciprocating piston arranged reciprocatingly in the cylinder and delimiting the combustion chamber;a crankcase attached to the cylinder;a crankshaft rotatably supported in the crankcase and driven by the piston;an intake passage supplying combustion air;an exhaust connected to the combustion chamber;a device for supplying fuel;a control device controlling the internal combustion engine;a pressure sensor for determining a crankcase pressure.

32. The internal combustion engine according to claim 31, wherein the pressure sensor is a relative pressure sensor.

33. The internal combustion engine according to claim 31, wherein the pressure sensor is arranged in the crankcase.

34. The internal combustion engine according to claim 31 in the form of a two-stroke engine, comprising at least one transfer passage connecting the crankcase to the combustion chamber, wherein the pressure sensor is arranged in the at least one transfer passage.

35. The internal combustion engine according to claim 31 in the form of a mixture-lubricated four-stroke engine having a lubricant reservoir connected to the crankcase, wherein the pressure sensor is arranged in the lubricant reservoir.

36. The internal combustion engine according to claim 31, comprising a temperature sensor measuring a crankcase temperature of the crankcase.

37. The internal combustion engine according to claim 36, wherein the temperature sensor is adapted to measure the average crankcase temperature.

38. The internal combustion engine according to claim 37, wherein the temperature sensor is arranged in a wall of the internal combustion engine and measures a temperature of the wall as said average crankcase temperature.

39. The internal combustion engine according to claim 36, wherein the pressure sensor and the temperature sensor are combined to a combined pressure/temperature sensor.

40. The internal combustion engine according to claim 30, wherein the device for supplying fuel is a fuel valve.