Method for determining an air mass in an internal combustion engine

Abstract

A method for determining a corrected air mass flow value in an engine having an air mass meter in its intake. The method includes determining a cold start condition of the engine at a first time when there is no air mass flow in the intake tract, producing a reference signal by the air mass meter at the first time, and determining an air mass flow offset from the reference signal, producing a measurement signal by the air mass meter at a second time, which is not equal to the first time, which is in an operating period of the engine, determining an air mass flow value from the measurement signal, and determining a corrected air mass flow value from the air mass flow offset and the air mass flow value.

Claims

1. A method for determining a corrected air mass flow value in an internal combustion engine, which has an air mass meter arranged in an intake tract of the internal combustion engine, the method comprising: determining a cold start condition of the internal combustion engine at at least one first time, at which there is no air mass flow in the intake tract, wherein determining the cold start condition comprises: determining that a temperature of the internal combustion engine is below a predetermined threshold temperature, and/or determining that the temperature of the internal combustion engine is in a predetermined range around an ambient air temperature; producing at least one reference signal by the air mass meter at the at least one first time; determining at least one air mass flow offset from the at least one reference signal of the air mass meter; producing a measurement signal by the air mass meter at at least one second time, which is not equal to the at least one first time and is in an operating period of the internal combustion engine; determining at least one air mass flow value from the measurement signal of the air mass meter; and determining the corrected air mass flow value from the at least one air mass flow offset and the air mass flow value.

2. The method as claimed in claim 1, further comprising: determining an air mass flow correction value from the at least one air mass flow offset.

3. The method as claimed in claim 2, wherein the air mass flow correction value is determined from a plurality of air mass flow offsets, which have been determined at a plurality of first times.

4. The method as claimed in claim 2, wherein the corrected air mass flow value is determined by subtracting the air mass flow correction value from the air mass flow value.

5. The method as claimed in claim 4, wherein a predetermined proportion of the air mass flow correction value determined is subtracted from the air mass flow value.

6. The method as claimed in claim 5, wherein the predetermined proportion is in a range of at least one of: approximately 50% to approximately 99%, and approximately 70% to approximately 95%.

7. The method as claimed in claim 5, wherein the predetermined proportion depends on a sensitivity and/or a raw characteristic curve of an air mass meter arranged to produce the measurement signal.

8. The method as claimed in claim 1, wherein determining the cold start condition further comprises: determining that an ignition of the internal combustion engine has been activated, and/or determining that a speed of the internal combustion engine is zero.

9. The method as claimed in claim 1, wherein determination of the at least one air mass flow offset and/or determination of the air mass flow value are/is based at least in part on a predetermined characteristic curve of the air mass meter.

10. The method as claimed in claim 9, wherein the predetermined characteristic curve of the air mass meter is at least partially nonlinear.

11. The method as claimed in claim 2, further comprising: determining the air mass flow correction value based in part on the determined air mass flow offset if the determined at least one air mass flow offset deviates by a predetermined value from the determined air mass flow correction value.

12. The method as claimed in claim 1, wherein the measurement signal and reference signal are sent as a Single Edge Nibble Transmission signal.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Further features and embodiments of the method according to the invention can be found with reference to the single drawing below. The FIGURE shows, by way of example, a diagram in which an illustrative air mass flow of an internal combustion engine is plotted against time.

DETAILED DESCRIPTION OF THE PRESENTLY PREFERRED EMBODIMENTS

(2) The FIGURE shows a diagram that illustrates, by way of example, three operating periods 10, 20, 30 of an internal combustion engine. During the three operating periods 10, 20, 30, different air mass flows and, consequently, different air mass flow values within the internal combustion engine occur.

(3) The first operating period 10 indicates the time interval between times t.sub.01, at which the speed of the internal combustion engine is still zero, and t.sub.10, at which the speed of the internal combustion engine is zero again. In a similar way, the second and third operating periods 20, 30 indicate time intervals between times t.sub.02 and t.sub.20 or between times t.sub.03 and t.sub.30.

(4) At a first time t.sub.11, a cold start condition of the internal combustion engine is detected. For example, it is determined that the ignition of the internal combustion engine has been activated and thus that, at this first time t.sub.11, there is now a current at an air mass meter arranged in an intake tract of the internal combustion engine. The air mass meter is designed to produce a signal that indicates the current air mass flow in the intake tract of the internal combustion engine. For example, the first time t.sub.11 is approximately 200 ms before time t.sub.01, at which the internal combustion engine is started.

(5) Consequently, a first reference signal is produced by the air mass meter at the first time t.sub.11 and is made available to the engine controller, for example. From the first reference signal produced at the first time t.sub.11, the engine controller can produce a first air mass flow offset. The first air mass flow offset is an air mass flow value which represents the air mass flow value incorrectly indicated by the air mass meter. The air mass flow offset is usually indicated in the unit [kg/h].

(6) During the first operating period 10, the air mass meter continuously produces measurement signals, which each indicate the current air mass flow within the intake tract of the internal combustion engine. For example, at a second time t.sub.21, which is not equal to the first time t.sub.11 and is in the first operating period 10, the air mass meter produces a measurement signal, which is made available to the controller of the internal combustion engine. From this measurement signal of the air mass meter, the controller determines a corresponding air mass flow value.

(7) The controller can then determine a corrected air mass flow value using the previously determined first air mass flow offset and the determined current air mass flow value for the second time t.sub.21. This is accomplished, for example, by subtracting the first air mass flow offset from the current air mass flow value.

(8) After the internal combustion engine has been switched off, the method can produce a new reference signal shortly before another cold start of the internal combustion engine at a further first time t.sub.12, from which the engine controller can determine a second air mass flow offset. The further first time t.sub.12 is also shortly before the cold start of the internal combustion engine of the second operating period 20 at time t.sub.02, e.g. 200 ms before time t.sub.02. During the second operating period 20, the controller can continuously determine corrected air mass flow values, e.g. at a further second time t.sub.22, taking account of the second air mass flow offset.

(9) The method can proceed in a similar way during the third operating period 30 of the internal combustion engine, wherein a third reference signal, from which a third air mass flow offset is determined, is produced by the air mass meter at a further first time t.sub.13. A corrected air mass flow offset can then be determined at the further second time t.sub.23, taking account of the third air mass flow offset.

(10) The method under consideration is preferably designed to determine an air mass flow correction value from the three air mass flow mass offsets, which have been determined at the three first times t.sub.11, t.sub.12, t.sub.13 and to use this air mass flow correction value in the respective operating cycles 10, 20, 30, instead of the respective air mass flow offset, to determine the corrected air mass flow value at the second times t.sub.21, t.sub.22, t.sub.23.

(11) In another embodiment, the full air mass flow offset, i.e. 100% of the respective air mass flow offset, can be used in each case in determining the corrected air mass flow value at the second times t.sub.21, t.sub.22, t.sub.23. However, this can lead to overcompensation of the error. For this reason, it is preferred that only a predetermined proportion of the respectively determined air mass flow offset be taken into account, e.g. subtracted, in determining the corrected air mass flow value. The predetermined proportion is approximately 80% of the respective air mass flow offset, for example.

(12) In the same way, the method can be designed to take into account only a proportion of the air mass flow correction value determined from the plurality of air mass flow offsets in determining the corrected air mass flow value, e.g. approximately 90%.

(13) In another advantageous embodiment of the method according to the invention, the air mass flow offsets determined can be evaluated in such a way that, if an air mass flow offset determined deviates by a predetermined value, e.g. by more than 50%, from the air mass flow correction value determined, this air mass flow offset determined is not incorporated into the continuous determination of the air mass flow correction value. Consequently, a deviating air mass flow offset of this kind is not stored. If the air mass flow correction value determined from a plurality of air mass flow offsets is approximately 5 kg/h, for example, but a new air mass flow offset determined is approximately 8 kg/h, the method can be designed not to incorporate this deviating air mass flow offset in the continuous averaging for the determination of the air mass flow correction value.

(14) Thus, while there have shown and described and pointed out fundamental novel features of the invention as applied to a preferred embodiment thereof, it will be understood that various omissions and substitutions and changes in the form and details of the devices illustrated, and in their operation, may be made by those skilled in the art without departing from the spirit of the invention. For example, it is expressly intended that all combinations of those elements and/or method steps which perform substantially the same function in substantially the same way to achieve the same results are within the scope of the invention. Moreover, it should be recognized that structures and/or elements and/or method steps shown and/or described in connection with any disclosed form or embodiment of the invention may be incorporated in any other disclosed or described or suggested form or embodiment as a general matter of design choice. It is the intention, therefore, to be limited only as indicated by the scope of the claims appended hereto.