JPH0633822A - Method of correcting position of reference mark - Google Patents

Abstract

PURPOSE: To accurately detect a reference mark and to continuously correct inaccuracy generated caused by friction by detecting the reference mark set corresponding to a predetermined position, i.e., a top dead point of an internal combustion engine, and correcting the position of the reference mark. CONSTITUTION: A pressure progress in a combustion chamber during non- combustion operation in a cylinder 20 of an internal combustion engine is obtained and stored depending on an angle of a crankshaft 14. An enantiomprphic progress is taken at a mirror mark 12 determined by the crankshaft angle. The enantiomprphic pressure progress is subtracted from the stored pressure progress in the combustion chamber to detect a first differential pressure progress. Further another differential pressure progress is detected at a position of a different mirror mark. These differential pressure progresses are compared with each other, and a position of a mirror mark with a differential pressure differing from zero for only a small predetermined value is determined as a top dead point, which is used to correct a position of its reference mark 13. Thus, a reference mark can be very accurately detected and continuously corrected.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention detects a reference mark provided at a predetermined position of an internal combustion engine, such as top dead center, by a detector, and triggers a detection pulse in an associated evaluation device. A certain reference mark position correction method.

[0002]

2. Description of the Related Art A sensor disk having at least one reference mark is fixed to a shaft of a crank shaft or a cam shaft of an internal combustion engine in order to detect the position of the shaft.
It is known to detect using a stationary detector. As the fiducial marks pass through the detector, they are successively detected by the evaluation circuit, which determines the position of the shaft.

A device for detecting the angular position of the shaft in this manner is known, for example, from EP 188433. The sensor disc described in this document has a number of markings of the same shape and one marking of a different shape. Markings of different shapes are used as reference marks. From the time sequence of angular mark edges of the same shape, reference mark detection is performed if at least one significant time difference occurs.

Such a known device has the following drawbacks. Thus, for example, the angle mark, which represents the reference mark, has the disadvantage that it must be constructed particularly precisely. This is because otherwise the position of the reference mark cannot be detected sufficiently accurately. However, the production of such a precise sensor disc is expensive. In addition, inaccuracies due to wear also occur in sensor discs manufactured very precisely.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to detect a reference mark provided at a predetermined position of an internal combustion engine, such as top dead center, by a detector, and to detect a detection pulse in an associated evaluation device. It is to improve the method of correcting the reference mark position that triggers as follows. In other words, even if a sensor disk manufactured with relatively low accuracy is used, the reference mark can be detected very accurately, and further, the inaccuracy caused by wear or the like can be continuously corrected.

[0006]

SUMMARY OF THE INVENTION According to the present invention, the above object is to obtain and store a pressure profile of a combustion chamber during non-combustion operation in at least one cylinder of an internal combustion engine depending on the crankshaft angle and store the same. A mirror image relationship is taken at a predetermined mirror mark, the pressure relationship having a mirror image relationship is subtracted from the stored pressure inside the combustion chamber to detect a first differential pressure history, and another differential pressure history is determined. Detecting at different positions of the mirror mark, comparing these pressure differentials with each other, the position of the mirror mark where the differential pressure is different from 0 by a small predetermined value is set to the top dead center, and the position of the reference mark is determined It is solved by using it for correction.

The method according to the invention has the following advantages: That is, there is an advantage that the reference mark can be detected very accurately even if a sensor disk manufactured with relatively low accuracy is used. Furthermore, the inaccuracies caused by wear are continuously corrected. For this purpose, a sensor disk with reference marks is detected by the sensor, and the pressure of the cylinder during non-combustion operation is determined and stored as a function of the crankshaft angle by means of one or more further sensors. The progress of the differential pressure is detected from the progress of the cylinder pressure as follows. That is, the differential pressure profile is detected by subtracting the mirror image pressure profile obtained using the mirror image relationship at the mirror mark from the stored cylinder pressure.

By appropriately moving the mirror mark, a number of different differential pressure profiles can be obtained. It is possible to set the top dead center by comparing these differential pressure processes with each other. This is because the mirror mark at the top dead center produces a differential pressure course which is slightly smaller than zero. The top dead center can be set by identifying the course of the differential pressure, and the position of the measured reference mark can be corrected accordingly.

It is possible to detect the exact position of the top dead center from the maximum value of the pressure having the pressure characteristic curve detected during the non-combustion operation. However, since the course of this maximum value is usually very flat, it is difficult to accurately detect the position. However, this is very easy when considering the differential pressure course. A particularly advantageous evaluation of the differential pressure profile is possible by integrating the differential pressure profile in a given crankshaft angular range and comparing the integrated values obtained by the integration with one another.

In addition, it is particularly advantageous if the method according to the invention for correcting the position of the reference mark can be carried out at selectable time intervals during operation of the internal combustion engine. To that end, all that needs to be detected is when the cylinder is in non-combustion or coasting operation.

Advantageous embodiments of the invention are described in the dependent claims.

[0012]

The present invention will be described in detail with reference to the drawings.

FIG. 1 shows an apparatus capable of implementing the method for correcting the position of a fiducial mark according to the invention. In this device, the control device is designated by 10. This controller performs all necessary calculations and storage operations in sequence.

The control device 10 is supplied with all the necessary information. The embodiment of FIG. 1 shows the sensor required for the present invention. In this case, the inductive sensor is shown at 11. This inductive sensor 11 scans a sensor disk 15 mounted on the shaft of an internal combustion engine, for example a crankshaft 14. This sensor disk 15 has a large number of marks 12 of the same shape on its surface and at least one reference mark 13 which is formed in the form of missing marks.

If desired, it is also possible to provide a number of fiducial marks that are different from each other or have the same shape. The number corresponds, for example, to the total number of cylinders or half the total number of cylinders.

When the crankshaft 14 rotates, the induction sensor 1
At 1, the voltage is induced as the mark 12 passes.
This voltage is evaluated in the control unit after signal processing. In this case, the rotational speed of the crankshaft 14 and the position of the reference mark 13 can be detected from the time intervals of the individual pulses, as is known.

The reference mark 13 clearly determines the position of the crankshaft 14. The reference mark 13 usually fixedly corresponds to the top dead center of the cylinder of the internal combustion engine. That is, a predetermined crankshaft angle-spacing with respect to the top dead center is obtained at the detected reference mark.

In addition to the signal supplied by the inductive sensor, the control unit 10 evaluates another signal. This further signal relates, for example, to the position of the accelerator pedal or the intake pipe pressure or temperature. These signals are sent to the sensors 16, 17, 1
8 (and possibly other sensors not shown here).

The pressure sensor 19 is arranged in one cylinder 20 of an internal combustion engine, not shown here. The pressure sensor 19 measures a combustion chamber pressure generated in the cylinder 20. It is also possible to arrange such a pressure sensor for each cylinder. Thereby, the combustion chamber pressure for each cylinder can be detected. Pressure sensor 19
The output signal of another pressure sensor (not shown) is also supplied to the control device and evaluated by this control device.

The control device 10 controls the internal combustion engine in dependence on the processed signal. This is indicated in FIG. 1 by the output 21 of the control device 10.

FIG. 2 shows the pressure p or the differential pressure d for different conditions as a function of the crankshaft angle KW (°). The characteristic curve A in the figure shows the pressure course in a normal combustion state. The maximum value of this characteristic curve A exists about 15 ° after the top dead center OT of the crankshaft angle.

Characteristic curve C shows the pressure profile in the cylinder when combustion is not taking place (for example in coasting of the internal combustion engine). In this case, the maximum value of the pressure characteristic curve is almost at the top dead center OT. This is a bit ahead for thermodynamic reasons.

Two methods are possible for detecting the differential pressure, ie the pressure caused by combustion. One method is to set the mirror mark SM in the region of the top dead center OT or exactly at the top dead center OT so that the pressure characteristic curve A has a mirror image relationship at the mirror mark SM. The characteristic curve B shows this mirror image relationship. Further, the differential pressure is obtained from the difference between the characteristic curve A and the characteristic curve C. This gives a curve of differential pressure. This is shown by the characteristic curve D.

On the other hand, when a difference between the characteristic curve A and the characteristic curve B is formed, the characteristic curve E of the differential pressure is obtained. The differential pressure is accurately detected by obtaining the differential pressure using the mirror mark SM (this is at the top dead center). This is because the pressure characteristic curve without combustion is symmetrical about the top dead center OT (as shown by the characteristic curve C, for example). The symmetry of the pressure characteristic curve in such non-combustion operation is used according to the invention to detect the exact position of the top dead center. This is done by the process described below.

The controller 10 identifies from the data provided by the individual sensors when one or more cylinders of the internal combustion engine are in a non-combustion state or a coasting state. This occurs when the fuel injection device or ignition device is shut off during engine braking operation.

In this case, the course of the differential pressure of the cylinder in the inertial operation state is detected according to the differential pressure detection method using the mirror mark shown in FIG.

In this case, the mirror mark is set at a position overlapping with the top dead center OT or at a position overlapping with the top dead center OT.

After the first differential pressure profile has been retrieved, the position of the mirror mark is changed (such a change can be made, for example, in one or more increments) and each differential pressure is detected and stored. It

In the next step, the mirror mark is moved in another direction. In this case, the measured value should be symmetrical at the first position of the mirror mark.

The mirror mark is placed at a position substantially corresponding to the top dead center in relation to the crankshaft position. The mirror mark then moves in the retard direction (with respect to terminology in the ignition system) and then in the advance direction. In this case, the differential pressure course is extracted for each position of each mirror mark.

FIG. 3 shows five different pressure differential curves. In this case, the characteristic curve F shows the differential pressure obtained at the position of the mirror mark near the top dead center. This mirror mark is in the correct position which can be used for correction. On the other hand, the characteristic curves G and H are moved in the retard direction, and the characteristic curves J and K are moved in the advance direction. The differential pressure due to the characteristic curve F deviates from the constant value or zero only slightly when observed over the time axis.
On the other hand, the differential pressure taken out by the mirror mark at the wrong place has a relatively large deviation.

For comparison, in FIG. 3 the characteristic curve C shows the pressure curve as a function of time (ie p
(T)).

According to the invention, it is assumed that the method works correctly and, in some cases, starting from the wrong starting position of the mirror mark, the symmetrical movement adjustment of the mirror mark is carried out over the following range: Becomes That is, it is premised that the process is performed over a range larger than the error range to be predicted when setting the reference mark.

If the characteristic curves F, G, H, E, K are integrated in the crankshaft angle range between approximately the top dead center OT and the crankshaft angle of 80 °, the integrated values obtained thereby are It can be used for: That is, it can be used to detect the correct position of the mirror mark and the top dead center or the correct position of the reference mark. If the mirror mark is in the right place, the integral should be minimal. The integrated value should be slightly negative considering the thermodynamic loss of the internal combustion engine.

The integrated value of the differential pressure belonging to the course of the differential pressure shown in FIG. 3 is shown in FIG. The integrated value belonging to the correct position of the mirror mark (which is indicated by the minimum integrated value) is shown by the characteristic curve L. In this case, this integrated value is obtained by integrating the characteristic curve F of FIG. 3 and is obtained for the correct position of the mirror mark.

If the top dead center OT is detected via the correct position of the mirror mark, it is possible to correct the position of the reference mark. This is because the distance between the reference mark and the top dead center is uniquely set in advance.

[0037]

The method according to the present invention has the following advantages. That is, the reference mark can be detected very accurately even if a sensor disk manufactured with relatively low accuracy is used. Further, according to the present invention, inaccuracies caused by wear or the like can be continuously corrected.

[Brief description of drawings]

FIG. 1 shows an advantageous device configuration for carrying out the method of the invention.

FIG. 2 is a diagram showing a pressure curve or a differential pressure curve as a function of a crankshaft angle (° KW).

FIG. 3 shows the pressure profile in non-combustion operation and the associated pressure profile at different mirror marks as a function of time.

FIG. 4 shows the integrated values of different differential pressure profiles as a function of time for comparison of pressure profiles in non-combustion operation.

[Explanation of symbols]

 10 Control Device 11 Induction Sensor 12 Mark 13 Reference Mark 14 Crankshaft 15 Sensor Disk 16 Sensor 17 Sensor 18 Sensor 19 Pressure Sensor 20 Cylinder 21 Output Side p Pressure d Differential Pressure

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Eckart Damson Germany Gerlingen Panora Mastrace 9 (72) Inventor Martin Klenk Germany Federal Republic of Germany Backnangstraßemannstrasse 11 (72) Inventor Martin Holt-Rossemann Federal Republic of Germany Ludwigsburg Hoffeldstrasse 15 (72) Inventor Vinfried Moser Germany Ludwigsburg Grundweinberge 14

Claims (8)

[Claims] 1. A detector detects a reference mark provided corresponding to a predetermined position of an internal combustion engine, such as top dead center, and triggers a detection pulse in an associated evaluation device.
In the correction method of the reference mark position, the pressure profile of the combustion chamber during non-combustion operation in at least one cylinder of the internal combustion engine is determined and stored depending on the crankshaft angle, and a mirror image relationship is obtained at a mirror mark determined by the crankshaft angle. And a first differential pressure profile is detected by subtracting the pressure profile in the mirror image relationship from the stored pressure profile in the combustion chamber, and another differential pressure profile at different mirror mark positions. In order to correct the position of the reference mark, the position of the mirror mark where the differential pressure is different from 0 by a small predetermined value is set as the top dead center. A method of correcting a reference mark position, which is used. 2. The correction of the reference mark position according to claim 1, wherein the position of the mirror mark is movable over a predetermined area, and this area is larger than the maximum predicted inaccuracy of the position of the reference mark. Method. 3. The reference mark position according to claim 2, wherein the mirror mark is placed at the center of the area, and is further moved symmetrically in two opposite directions to detect the differential pressure for each position of the mirror mark. Correction method. 4. The method of correcting the reference mark position according to claim 3, wherein the movement of the mirror mark is performed by an increment. 5. The method according to claim 1, wherein the differential pressure profiles obtained for different mirror marks are integrated, the integrated values are compared with each other, and the top dead center is identified depending on the integrated value. The method for correcting the reference mark position according to any one of claims 1. 6. The predetermined integral of the crankshaft angle range,
The method for correcting the reference mark position according to claim 5, wherein the correction is performed in a range between the top dead center and the crankshaft angle of 80 °. 7. The correction according to claim 1, wherein the non-combustion phase is identified, and the correction is performed each time a predetermined time has elapsed.
The method of correcting the reference mark position according to any one of items 1 to 3. 8. The method for correcting the reference mark position according to claim 1, wherein the evaluation is performed by a control device for an internal combustion engine.