Method for determining an average segment time of an encoder wheel of an internal combustion engine

Abstract

A method for determining an average segment time of an encoder wheel of an internal combustion engine, the encoder wheel being connected in rotationally fixed fashion to a crankshaft of the internal combustion engine, markings being situated along the circumference of the encoder wheel, and the crankshaft of the internal combustion engine passing through specified angular ranges during segment times, segment times being acquired, associated rotational speed values being determined from the segment times, a rotational speed curve being determined from the individual determined rotational speed values, a value of the average rotational speed being determined from the rotational speed curve, and an average segment time being determined from the value of the average rotational speed.

Claims

1. A method for determining an average segment time of an encoder wheel of an internal combustion engine, the method comprising: operating the internal combustion engine in a coasting operation or in a freely falling operation or with a large rotational speed gradient; while the internal combustion engine is operating in the coasting operation or in the freely falling operation or with the large rotational speed gradient, acquiring segment times using a sensor, via a control device, wherein the encoder wheel is connected in a rotationally fixed manner to a crankshaft of the internal combustion engine, markings being situated along a circumference of the encoder wheel, and the crankshaft of the internal combustion engine passing through specified angular ranges during segment times; determining, via the control device, associated rotational speed values from the segment times; determining, via the control device, a rotational speed curve over time from the individual ones of the determined rotational speed values; determining, via the control device, a value of an average rotational speed from the rotational speed curve; determining, via the control device, an average segment time from the value of the average rotational speed; and controlling the internal combustion engine using the determined average segment time, the controlling including regulating uneven running of the internal combustion engine based on the determined average segment time.

2. The method of claim 1, wherein the rotational speed curve over time is determined as a best-fit curve through the individual determined rotational speed values over a working cycle of the internal combustion engine.

3. The method of claim 2, wherein the average rotational speed is determined from the rotational speed curve using a linear or quadratic regression method, or using a method of least squares.

4. The method of claim 1, wherein a difference is determined of a currently acquired segment time and the determined average segment time.

5. The method of claim 1, wherein there is a calibration of a pre-injection of the internal combustion engine.

6. A computing unit for determining an average segment time of an encoder wheel of an internal combustion engine, comprising: a computing arrangement configured to perform the following: operating the internal combustion engine in a coasting operation or in a freely falling operation or with a large rotational speed gradient; while the internal combustion engine is operating in the coasting operation or in the freely falling operation or with the large rotational speed gradient, acquiring segment times using a sensor, wherein the encoder wheel is connected in a rotationally fixed manner to a crankshaft of the internal combustion engine, markings being situated along a circumference of the encoder wheel, and the crankshaft of the internal combustion engine passing through specified angular ranges during segment times; determining associated rotational speed values from the segment times; determining a rotational speed curve over time from the individual ones of the determined rotational speed values; determining a value of an average rotational speed from the rotational speed curve; and determining an average segment time from the value of the average rotational speed; and controlling the internal combustion engine using the determined average segment time, the controlling including regulating uneven running of the internal combustion engine based on the determined average segment time.

7. The method of claim 1, wherein the rotational speed curve over time is determined as a best-fit curve through the individual determined rotational speed values over a working cycle of the internal combustion engine, wherein a difference is determined of a currently acquired segment time and the determined average segment time, and wherein there is a calibration of a pre-injection of the internal combustion engine.

8. The method of claim 7, wherein the average rotational speed is determined from the rotational speed curve using a linear or quadratic regression method, or using a method of least squares.

9. A non-transitory computer readable medium having a computer program, which is executable by a processor, comprising: a program code arrangement having program code for determining an average segment time of an encoder wheel of an internal combustion engine, by performing the following: operating the internal combustion engine in a coasting operation or in a freely falling operation or with a large rotational speed gradient; while the internal combustion engine is operating in the coasting operation or in the freely falling operation or with the large rotational speed gradient, acquiring segment times using a sensor, via the processor, wherein the encoder wheel is connected in a rotationally fixed manner to a crankshaft of the internal combustion engine, markings being situated along a circumference of the encoder wheel, and the crankshaft of the internal combustion engine passing through specified angular ranges during segment times; determining, via the processor, associated rotational speed values from the segment times; determining, via the processor, a rotational speed curve over time from the individual ones of the determined rotational speed values; determining, via the processor, a value of an average rotational speed from the rotational speed curve; and determining, via the processor, an average segment time from the value of the average rotational speed; controlling the internal combustion engine using the determined average segment time, the controlling including regulating uneven running of the internal combustion engine based on the determined average segment time.

10. The computer readable medium of claim 9, wherein the rotational speed curve over time is determined as a best-fit curve through the individual determined rotational speed values over a working cycle of the internal combustion engine.

11. The computer readable medium of claim 10, wherein the average rotational speed is determined from the rotational speed curve using a linear or quadratic regression method, or using a method of least squares.

12. The computing unit of claim 6, wherein the rotational speed curve over time is determined as a best-fit curve through the individual determined rotational speed values over a working cycle of the internal combustion engine.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 schematically shows a configuration fashioned in order to execute a specific embodiment of a method according to the present invention.

(2) FIG. 2 shows schematic diagrams that can be determined in the course of a specific embodiment of a method according to the present invention.

DETAILED DESCRIPTION

(3) In FIG. 1, a system fashioned to execute a specific embodiment of a method according to the present invention is shown schematically.

(4) An encoder wheel 10 is connected to a crankshaft 11 of an internal combustion engine (not shown in FIG. 1) of a motor vehicle. The circumference or edge of encoder wheel 10 has markings (teeth) symbolically designated by the four reference characters 12a, 12b, 12c, and 12d. The markings can be configured, for example for 60 or 60-2 teeth, with a respective spacing of 6.

(5) Encoder wheel 10 can be divided into a plurality of segments, in particular essentially equidistant from one another. In the specific example of FIG. 1, encoder wheel 10 is divided into two segments SA and SB, each 180, between marking 12a and marking 12e.

(6) For example, in an internal combustion engine having four cylinders, a segment SA or SB corresponds to a crankshaft movement of 180 and a piston stroke of a piston of the internal combustion engine. Here, a piston stroke is to be understood as the movement of the piston between top dead center OT and lower dead center UT.

(7) A sensor is fashioned as a Hall sensor 13. Hall sensor 13 is situated close to the edge of encoder wheel 10, and is connected with a line 14 to a control device 15 of the internal combustion engine. Control device 15 is set up to carry out a specific embodiment of a method according to the present invention.

(8) During operation of the internal combustion engine, crankshaft 11 rotates, and encoder wheel 10 also rotates therewith. The beginning of each marking produces a voltage pulse in sensor 13. An associated voltage signal is shown schematically in FIG. 1 as diagram U(t).

(9) Control device 15 evaluates voltage signal U(t) and determines therefrom the segment times as differences in the times at which the voltage pulses of the corresponding markings of the encoder wheel, in this example markings 12a and 12e, were acquired. In addition, control device 15 executes a specific embodiment of a method according to the present invention explained on the basis of FIG. 2. In FIG. 2, diagrams are shown schematically that can be determined in the course of a specific embodiment of a method according to the present invention.

(10) Diagram 210 describes the first method step of the method according to the present invention, and shows a diagram of segment times s plotted over time t. Diagram 210 thus shows a temporal curve of the acquired segment times. Here, the internal combustion engine is in coasting operation, in which, when the frictional power connection is not separated, the internal combustion engine is kept in rotational motion. The rotational speed decreases rapidly and a comparatively large rotational speed gradient n occurs. For example, in the following example a rotational speed gradient of n=1500 RPM/s is assumed. The value of successive segment times increases accordingly. As is shown in diagram 210, the values of segment times s.sub.1 to s.sub.5, acquired at times t.sub.1 to t.sub.5, increase. The segment times however do not increase in linear fashion, but rather in approximately hyperbolic fashion.

(11) According to the present invention, the segment times are therefore converted into rotational speed values n. This can take place for example using the designation n=N/s, where N is the standard number of markings of the encoder wheel.

(12) The rotational speed values n.sub.1 to n.sub.5 associated with times t.sub.1 to t.sub.5, determined from segment times s.sub.1 to s.sub.5, are shown in diagram 220 in a rotational speed-time diagram. In the next method step, a best-fit curve is then plotted via rotational speed values n.sub.1 to n.sub.5. In this specific example, this takes place using a linear regression method.

(13) In diagram 230, which shows a rotational speed-time diagram analogous to diagram 220, the best-fit curve is shown as best-fit straight line 231. Because the rotational speed gradient runs in linear fashion, best-fit straight line 231 can be plotted through the rotational speed values with a high degree of precision and low error. In addition, an average value of the rotational speed can be extrapolated with a high degree of precision. In the diagram, such an extrapolated value is shown for average rotational speed n* at a time t*. Time t* can be a current time for which the current value of average rotational speed n* is determined. Time t* can also be a future time for which a future value of average rotational speed n* is estimated. The value of rotational speed n* is finally converted again into a segment time, and is determined as average segment time s*=N/n*.