Method and control device for operating an internal combustion engine

Abstract

A method for operating an internal combustion engine, such as a marine diesel engine, that is operative for rotating an output shaft of the engine in a normal operating mode for generating a desired output power based on an operating fuel quantity introduced into the engine. The engine is operated in a calibration mode at a defined rotational speed of the output shaft, and a calibrating fuel quantity introduced into the engine to maintain the defined rotational speed in the calibration mode is determined. In the normal operating mode of the engine, the engine output power is determined based on the operating fuel quantity being introduced into the engine in the normal operating mode and the calibrating fuel quantity determined in the calibration mode.

Claims

1. A method for operating an internal combustion engine, that is operative for rotating an output shaft of the engine, to enable selective operation of the engine in a normal operating mode for generating a desired output power by introducing a suitable quantity of operating fuel into the engine, comprising the steps of: operating the engine in the normal operating mode at least at a defined rotational speed and at zero load to determine an initial output power to operating fuel quantity relationship; storing the initial output power to operating fuel quantity relationship; operating the engine in a calibration mode by operating the engine so that the engine output shaft rotates at the defined rotational speed and at zero load; determining, in the calibration mode operation of the engine, a calibrating fuel quantity comprising the quantity of fuel being introduced into the engine to operate the engine at the defined rotational speed during the calibration mode at zero load; determining a fuel quantity calibration offset based on the calibrating fuel quantity; determining, in the normal operating mode of the engine, the output power being generated by the engine as a function of: the determined calibrating fuel quantity at the defined rotational speed and at zero load and the quantity of operating fuel being introduced into the engine in the normal operating mode at the defined rotational speed and at zero load; and operating the internal combustion engine at a modified output power to operating fuel quantity relationship comprising the initial output power to operating fuel quantity relationship and the calibration offset.

2. A method in accordance with claim 1, wherein said determining of the output power in the normal operating mode of the engine comprises determining the output power using a characteristic curve dependent on the operating fuel quantity introduced into the engine, the characteristic curve being calibrated using the determined calibrating fuel quantity.

3. A method in accordance with claim 2, wherein said determining of the output power in the normal operating mode of the engine comprises determining the output power based on a linear dependency of the operating fuel quantity introduced into the engine and the output power.

4. A method in accordance with claim 3, wherein the linear dependency comprises:
P=a+b*E, wherein P is the output power of the engine, E is the operating fuel quantity and a and b are constants of the linear dependency, and wherein the constant a is determined based on the determined calibrating fuel quantity.

5. A method in accordance with claim 1, wherein in the calibrating mode of the engine the engine is operated in an output shaft rotational speed-controlled manner.

6. A method in accordance with claim 1, wherein the engine is operated in the calibration mode immediately after start-up of the engine.

7. A method in accordance with claim 1, further comprising the step of correcting the determined calibrating fuel quantity based on at least one of a measured fuel viscosity, a calculated fuel viscosity, a measured fuel temperature, and a calculated fuel temperature.

8. A control device of an internal combustion engine, comprising an automated controller for carrying out the method of claim 1.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) In the drawings:

(2) FIG. 1 graphically depicts a linear relationship characteristic plot of engine power (P) vs operating fuel quantity (E); and

(3) FIG. 2 diagrammatically depicts a control device for implementing and carrying out the method of the invention.

DETAILED DESCRIPTION OF THE PRESENTLY PREFERRED EMBODIMENTS

(4) The present invention relates to a method for operating an internal combustion engine, in particular a large engine such as a marine diesel-type internal combustion engine, and to a control device for implementing and carrying out the inventive method.

(5) In a normal or regular operating mode of an internal combustion engine, fuel is introduced, as for example injected, into cylinders of the engine with the assistance of a fuel supply system. The operating fuel quantity introduced into the internal combustion engine can be determined and, dependent on the fuel quantity so introduced, the output power currently being generated or made available by the engine in its normal operating mode can be determined.

(6) FIG. 1 is a graph depicting the relationship of a characteristic 10, with the assistance of which the power P made available by the internal combustion engine in its normal operating mode can be determined as a function of the operating fuel quantity E that is introduced into the internal combustion engine. As will be apparent, the characteristic 10 depicted in FIG. 1 is a linear dependency between the operating fuel quantity E and the output power P that is generated by the engine.

(7) The output power P of the internal combustion engine is thus determined in the normal operating mode of the engine using the characteristic 10, which is based on the following linear dependency:
P=a+b*E,

(8) wherein E is the operating fuel quantity, and a and b are constants of the linear dependency.

(9) In FIG. 1, the constant a corresponds to the fuel quantity required by the internal combustion engine in no-load operation, i.e. with zero load. The constant b corresponds to the gradient of this linear dependency.

(10) The available output power P can also be determined on the basis of the operating fuel quantity E that is introduced into the internal combustion engine even via a non-linear dependency for a particular usage or application.

(11) In accordance with the inventive method, the internal combustion engine output shaft is operated at a defined rotational speed in a calibration mode, and the calibrating fuel quantity used by the engine to maintain that speed is determined. Preferably, the internal combustion engine is operated in this calibration mode at a defined idle rotational speed at zero load, i.e. in a no-load operating condition or mode. Thus, the calibrating fuel quantity that the internal combustion engine requires to maintain the idle rotational speed at zero load is determined in this calibration mode of engine operation.

(12) Utilizing a linear dependency between the available engine output power P and the operating fuel quantity E introduced into the engine in the calibration mode, as shown in FIG. 1, enables calculation of the constant a of the linear dependency and, thereby, calibration of the linear dependency of FIG. 1. Two constants a1 and a2 are identified in FIG. 1, wherein the calibrated characteristic 10 is obtained by a parallel shift of the previously valid characteristic 10 such that the calibrated characteristic 10 runs through the value a2 which has been determined in the current or most recent calibration mode operation. The value a2 corresponds to the calibrating fuel quantity, which the internal combustion engine requires at zero load for maintaining the defined idle rotational speed.

(13) It is further preferred that, in the calibration mode of the internal combustion engine, the engine is operated in a rotational speed-controlled manner.

(14) The calibration mode of the internal combustion engine is preferentially initiated immediately following engine start-up in order to recalibrate the characteristic for determining the available output power P after every start-up of the engine and to thus ensure optimal operation of the engine when it is then operated in its normal operating mode.

(15) The present invention renders possible, in the normal operating mode of an internal combustion engine, a more accurate determination of the available engine output power, based on the quantity of fuel being delivered or input to the engine, than is attainable in accord with the prior art. In particular, inaccuracies resulting from fuel fluctuations and/or wear in the fuel supply system can be effectively eliminated by implementing the calibration mode output power determination of the present invention.

(16) In accordance with a further advantageous feature of the invention, the calibrating fuel quantity determined in the calibration mode can be corrected on the basis of a calculated and/or measured fuel viscosity and/or on the basis of a measured and/or calculated fuel temperature, thereby eliminating the influences of these factors or characteristics as the engine output power relationship is calculated and determined in the calibration mode of the inventive method and further enhancing the accuracy of the calculated dependency of output power as a function of operating fuel quantity during normal engine operation.

(17) A control device constructed in accordance with the invention is implemented as an automated or semi-automated controller or controller means for carrying out the inventive method as herein described. The controller or controller means 20, diagrammatically depicted in FIG. 2, includes data interfaces for data exchange between the assembliessuch as sensorsinvolved in implementing and carrying out the method, a data storage unit for storage of data, and a processor for processing of the data, and may be constructed of known parts or elements or subassemblies as a general matter of design choice suitable, as will be apparent to those of ordinary skill in the art, to carry out the method of the invention.

(18) While there have been shown and described and pointed out fundamental novel features of the invention as applied to preferred embodiments thereof, it will be understood that various omissions and substitutions and changes in the form and details of the methods and devices described, and in their practice and operation, may be made by those skilled in the art without departing from the spirit of the invention. It is the intention, therefore, to be limited only as indicated by the scope of the claims appended hereto.