DE102008032026A1 - Cam shaft sensor unit for determining absolute position of cam shaft, has sensor wheel distributing multiple trigger fingers on circumference, where number of fingers determines angle recognition accuracy which is less than specific degree - Google Patents

Abstract

The unit (1) has a sensor wheel (3) fastened to a cam shaft (2), a sensor (4) that is aligned on the sensor wheel and an evaluation unit. The sensor wheel distributes multiple trigger fingers (6) on a circumference and comprises a label, where the number of trigger fingers determines angle recognition accuracy which is less than 20 degree. The label is arranged on an axially shifted trace on the sensor wheel. The sensor wheel is a magnetic pole ring with an alternating polarized permanent magnet as trigger. An independent claim is also included for a method for controlling an electromechanical cam shaft adjuster of an internal combustion engine during engine start.

Description

Field of the invention

The The invention relates to a camshaft sensor unit for determination an absolute position of a camshaft at low speeds and a method of controlling an electromechanical camshaft adjuster an internal combustion engine at engine start.

The The invention preferably relates to electromechanical camshaft adjusters and non-locking hydraulic phaser since the locking hydraulic phaser due to the lack of oil pressure locked at engine start, d. H. this during the Engine starts can not adjust.

While the starting of the internal combustion engine should be the electromechanical Camshaft adjuster the desired adjustment so adjust as quickly as possible, with a defined control only with known absolute position of the camshaft at engine start or at a known adjustment angle at engine start possible is.

In WO 2005/012698 A1 discloses an apparatus and method for determining the angle of rotation between two shafts, in particular between a camshaft and a crankshaft. The angle of rotation of the camshaft is computationally zählerbasiert or time-based calculated from signals of the crankshaft trigger wheel and the commutation signals of the servo motor. Various stop strategies are described. As a design variant of the device, the possibility is mentioned to use active sensors together with a storage medium for determining and storing the absolute position of the camshaft, wherein an active sensor generally has its own power supply and a signal corresponding to the state of the quantity to be detected signal regardless of State of an environment size, e.g. B. movement of a sensor target wheel generated.

US Pat. No. 7,243,627 B2 discloses a method for controlling the displacement of an electromechanical camshaft adjuster. The actuating shaft of the camshaft adjuster is connected to an electric motor, which is arranged in a three-shaft gear for setting the desired adjustment angle between the camshaft and crankshaft. The angle of rotation of the crankshaft is detected by means of a sensor arranged on the electric motor, wherein the electric motor is not operated at low speeds, that is, the camshaft adjuster is not adjusted. Thus, the angle of rotation of the electric motor corresponds to the angle of rotation of the crankshaft. The sensor detects the angle of rotation and the direction of rotation of the crankshaft, wherein the absolute position of the crankshaft when switching off the engine is determined and stored for the restart. The stored crankshaft position is used to control ignition and fuel injection until a defined crankshaft position has been detected for the first time after engine restart. The method provides a solution for controlling the displacement of an electromechanical camshaft adjuster in the running internal combustion engine. A control of the adjustment angle at engine start is not possible.

From the DE 10 2006 017 232 A1 For example, a synchronization device for an internal combustion engine is known which has a first active sensor and a second active sensor. The active sensors are used to detect the angular positions of the crankshaft and camshaft and provide the controller information about the state of the angular positions of the waves or the phase relationship between the waves during an engine stop phase ready. The goal is to maintain the desired phasing between camshaft and crankshaft even during the stop phase and during standstill to achieve a short startup time for the next engine start. During normal operation of an internal combustion engine, the angular position of the cam and crankshaft or the adjustment angle between the two is detected by means of trigger wheels fixed to the camshaft and crankshaft, wherein the angular position is calculated on the basis of a mark on the trigger wheel. To do this, a camshaft sensor generates trigger wheel signals that are processed in combination with similar signals from the crankshaft in the controller to determine the absolute position of the camshaft. The disadvantage of the method for synchronizing two waves from the cited patent is that when the engine is started, the mark on the trigger wheel should first be recognized by the control unit software in order to calculate the angular position of the shafts or the adjustment angle between the two. At engine start, the crankshaft speed is very slow (typically 200 degrees crankshaft / min). This means that the time between two trigger signals and thus the time interval until the detection of the angular position of the waves or the adjustment angle is very long.

While the start of the internal combustion engine is without the use of start / stop strategies in the system, the current position of the camshaft adjuster not known. Therefore, the adjuster is usually "blinded", until a mechanical limit stop is reached and from the control unit was detected. Only then is the position of the adjuster known and the desired adjustment angle can be adjusted

While the starting of the internal combustion engine to the camshaft adjuster the desired adjustment angle as fast as possible reach, so that the exhaust emissions and / or smoothness of the internal combustion engine can already be optimized at engine start. Quick Start Applications are desired to complete the compression cycle to optimize in the cylinders at engine start, resulting in a faster Start with reduced power requirements leads.

The It is therefore an object of this invention to provide a device and to provide a method that allows the needed Time to set the desired adjustment angle of a shorten the electromechanical camshaft adjuster at engine start.

The The object is achieved by a camshaft sensor unit according to claim 1 and by a method of controlling an electromechanical Camshaft adjuster solved according to claim 12.

advantageous Embodiments of the invention are in the subclaims specified.

The inventive method provides that a absolute position of a camshaft when switching off an internal combustion engine is detected and stored so that they are read out at a new engine start and used to control a camshaft adjuster can. The actual displacement angle of the camshaft adjuster is at Engine start based on the read out absolute position of the camshaft determined. A desired displacement angle of the camshaft adjuster for the engine start is known. According to the invention a control angle from the difference of the desired adjustment angle and of the actual adjustment angle and for controlling the actuator used a control shaft. This shortens advantageously clearly the time to set the desired adjustment angle, because the camshaft adjuster immediately after the start of the engine is controllable.

The Detection of the absolute position of the camshaft is performed by a Camshaft sensor unit according to the invention with one attached to the camshaft sender wheel, at least one active sensor and an evaluation unit.

The Transmitter wheel according to the invention has on its circumference Distributes a number of triggers and at least one marker where an angle detection accuracy determined by the number of triggers less than 20 ° NW (degree camshaft). The higher the number of triggers is chosen, the higher the angular recognition accuracy, in particular at very low speeds.

In a particularly preferred embodiment has the Encoder wheel 36 trigger. That is a resolution of 10 ° NW per trigger and gives an angle detection resolution of +/- 5 ° NW.

The Relationship between trigger and absolute camshaft position is by the geometry or the assembly of the internal combustion engine fixed and freely selectable with the trigger number.

The Brand can be arranged on the sender wheel or in a separate lane be. The mark is used to detect a full rotation of the camshaft.

The Arrangement of the mark on a separate track has the advantage that in the range of the mark the angular accuracy is maintained, because the width of all triggers can stay the same. A second track offers In addition, the possibility of multiple brands, for example one for each cylinder.

Of the active sensor is preferably radially opposite arranged the encoder wheel and detects the passing him triggers of the rotating on the camshaft sensor wheel.

Of the used sensor is on the sender wheel and the shape of the trigger vote. For example, inductive, hall effect-based or magnetoresistive sensors are used.

In a preferred embodiment of the invention, two active sensors are arranged offset by an angle θ to each other on the encoder wheel, so that the sensor signals generated by them temporally ver can be received in the evaluation unit. This arrangement allows the detection of a reversal of the direction of rotation of the camshaft. In one direction of rotation, the signal of the first sensor is detected in time before the signal of the second sensor, in the opposite direction of rotation first the second signal and then the first signal is detected.

Of the Angle θ can be chosen freely, provided that that the signals of the two sensors are not identical in the two Directions are. That is, θ may not be the width of a trigger nor the distance between two triggers (or a multiple thereof).

The absolute position of the camshaft is based on the sensor signals determined in the evaluation, here also the direction of rotation the trigger wheel is detected and taken into account. A advantageous variant of the determination of the absolute position becomes explained in detail later.

In In a preferred embodiment, the sender wheel is a Trigger wheel with trigger fingers, which by an inductive or magnetoresistive sensor can be detected. The number of on the Scope distributed trigger finger determines the angle detection resolution.

The Transmitter wheel is in another preferred embodiment designed as a gear, the two sensors are each offset by half a tooth. This and the shape of the Teeth are selected so that the sensor signals Sinusoidal signals are. The displacement by half a tooth will be in the evaluation unit receive a sine and a cosine signal.

This allows the determination of the current angle between the teeth of the gear in the evaluation unit, what the Increase in the angle recognition accuracy contributes.

The Tuning of trigger shape and sensor may be in other embodiments be made in such a way that a continuous, harmonious and decaying signal level or a harmoniously changing signal level is produced. An accurate determination of the position of the camshaft is possible as well.

Of course can digitization before further processing of the sensor signals respectively.

In a further preferred embodiment of the invention the encoder wheel is a magnetic pole ring with alternating polarization on the circumference as a trigger, wherein also with the magnetic pole ring sinusoidal Sensor signals can be generated.

The Transmitter wheel may also be considered otherwise in other embodiments magnetically coded track be executed.

The Encoder wheel can be made in one piece with the camshaft be.

Become used two active sensors, these can be separate or arranged in a common sensor housing on the trigger wheel become.

advantageously, Filtering of the sensor signals to improve the signal quality.

The The camshaft sensor unit according to the invention can together with a similar sensor unit to the crankshaft be used, with the absolute position of the camshaft based by the camshaft sensor unit and the similar sensor unit Sen sorsignale generated in the evaluation unit on the crankshaft is determined. In addition, control signals for Compensation of an angle error due to elongation of the drive and chain tensioner state are generated.

Further Details, features and advantages of the invention on the basis advantageous embodiments will become apparent from the following Description of the figures. These show with schematic representation in

1 a first embodiment of a camshaft sensor unit according to the invention;

2 a cross-sectional view of a camshaft sensor unit and a diagram of the associated sensor signals and the speed of the trigger wheel as a function of time;

3 a second embodiment of a camshaft sensor unit in various representations;

4 Time curves of the sensor signals from the camshaft sensor unit according to 3 to be delivered;

5 a waveform diagram (!);

6 a cross-sectional view of a third preferred embodiment of a camshaft sensor unit;

7 A fourth preferred embodiment of a camshaft sensor unit in various views.

1 Fig. A) shows a three-dimensional view of a first embodiment of a camshaft sensor unit according to the invention 01 for determining an absolute position of a camshaft 02 an internal combustion engine at low speeds or at engine stop / start for an electromechanical cam shaft adjuster. The camshaft sensor unit 01 includes one on the camshaft 02 attached donor wheel, which serves as a trigger wheel 03 is executed. The trigger wheel 03 can on the camshaft 02 mounted or in one piece with the camshaft 02 be executed. A sensor 04 is at the trigger wheel 03 positioned and attached, for example, to the cylinder head of the engine.

The camshaft sensor unit 01 preferably also includes an unillustrated storage medium, which determines the determined absolute position of the camshaft 02 when switching off the internal combustion engine for the next start of the engine stores. The storage medium may also be provided in the control device of the camshaft adjuster.

The trigger wheel 03 is inventively with much more triggers, which as a trigger finger 06 are designed as usual in the art, and at least one unique brand 07 applied per revolution. The execution of the trigger wheel 03 with the brand 07 as well as the positioning of the sensor 04 on the trigger wheel 03 can be seen from Fig. b) and c), which is a side view and a top view of the camshaft sensor unit 01 out 1 , Fig. A) represents.

When starting the engine, it is not enough, "any" trigger finger 06 to be able to recognize, but the evaluation unit must "know" which Triggerfinger 06 Was seen. That's why the brand is unique 07 provided on the camshaft pulley to the absolute position of the camshaft 02 using the trigger finger 06 on the trigger wheel 03 to be able to determine. This brand 07 is called a "top dead center mark" or "OT mark", which by its different width compared to the other trigger fingers 06 is recognized. Alternatively, the unique brand 07 course be replaced by a unique gap, which is recognized by their different width compared to the other trigger gaps.

This allows each trigger finger in the evaluation unit 06 be assigned a serial number, which is an absolute position of the camshaft 02 equivalent. z. For example, the following logic could occur in the evaluation unit:

When detecting a trigger finger 06 : Is the trigger finger the mark? 07 ? then finger number = 0 Is the trigger finger not the mark 07 ? then finger number = finger number + 1

The relationship between the trigger wheel 03 and the absolute position of the camshaft 02 is determined by the mechanical geometry or assembly of the engine and selectable, z. With 36 fingers: brand 07 (Finger 0) 0 ° NW (or 0 ° KW) Finger 1 10 ° NW (or 20 ° KW) Finger 2 20 ° NW (or 40 ° CA) Finger 3 ...

Furthermore, the selection depends on the number of trigger fingers 06 to the desired angle identification accuracy or resolution. This is z. For example, for stop-start and quick-start applications typically ± 3 ° CA (crankshaft grade). Relative to the camshaft (crankshaft degree = 2 × camshaft degree), this means that the position of the camshaft 02 every 3 ° NW (camshaft degree) is detected or the angle detection resolution is 3 ° NW.

The maximum possible number of trigger fingers 06 is dependent z. B. of the sensor used 04 and / or the ambient conditions, such as installation space, air gap fluctuations between sensor 04 and trigger wheel 03 or positioning accuracy of the sensor 04 to the trigger wheel 03 ,

In the illustrated preferred embodiment, the camshaft sensor unit is 01 executed with two offset to each other arranged active sensors, which is the speed of the camshaft 02 until motor standstill can be detected (ie up to 0 1 / min). The same applies when starting the engine. There are different possibilities, eg. B. active Hall sensors, active inductive sensors, magnetoresistive sensors. The integration of the two sensors in the camshaft sensor unit 01 offers the advantages of increasing the positioning accuracy of the two sensors, simplifying assembly (using only one sensor instead of two), minimizing the installation space of the sensors (and the associated fixings). Alternatively, the sensor 04 or parts thereof are integrated in a component of a camshaft adjuster or in another attachment component. Alternatively, of course, the trigger wheel 03 be integrated into a camshaft-fixed component of a camshaft adjuster or other attachment component.

A focus of the camshaft sensor unit according to the invention 01 lies in the reverse rotation detection of the camshaft 02 and the associated determination of the absolute position of the camshaft 02 , At engine stop, it often happens that the camshaft 02 a slight reverse rotation (ie a rotation in the opposite direction to the normal direction of rotation of the camshaft 02 ) power. Without this possible reverse rotation of the camshaft 02 It is not possible to detect the absolute end position of the camshaft 02 to be determined at engine stop or start.

The procedure for detecting a reverse rotation in the evaluation unit is based on the in 2 shown cross section (Fig. A) of a camshaft sensor unit 01 with a rotating 6-finger trigger wheel known in the art 11 and a diagram (Figure b) of the associated sensor signals 13 . 15 and the speed 23 of the 6-finger trigger wheel 11 as a function of time t.

The arrangement comprises a sensor 04 with two integrated staggered individual sensors, which on the 6-finger trigger wheel 11 is arranged.

For a better understanding of the process here is a 6-finger trigger wheel 11 selected. Of course, it is usable with the high number of triggers according to the invention.

The in the sensor 04 integrated two active individual sensors are offset to each other so that even those of them generate sensor signals 13 and 15 are also correspondingly at least offset in time. The sensor signals 13 . 15 are shown in the corresponding diagram as a function of time. In addition to the sensor signals 13 . 15 is the speed 23 of the 6-finger trigger wheel 11 shown as a function of time t to the waveform when a change in the direction of rotation of the camshaft 02 to clarify.

Between the two active individual sensors of the sensor 04 there is an angular offset θ. The angular offset can be chosen freely with the condition that the sensor signals 13 . 15 are not identical in the two directions. ie, the angular offset θ may not be the width (or multiple) of a trigger finger 06 still the width of a trigger finger 06 until the next trigger finger 06 (or multiple). For example, the angular offset θ may be for a trigger wheel 03 with 36 trigger fingers 06 not 5 ° NW or a multiple of 5 ° NW.

The angular offset θ causes clockwise sensor signal in the direction of rotation 15 according to sensor signal 13 is seen. In the counterclockwise direction of rotation, the sensor signal is detected 13 after the sensor signal 15 ,

The direction of rotation of the 6-finger trigger wheel 11 is determined by the order of the sensor signals 13 . 15 by means of a camshaft sensor unit 01 connected evaluation unit, not shown, detected. The principle is identical for a trigger wheel 03 with much more trigger fingers 06 ,

3 Fig. A) shows a three-dimensional view of a second preferred embodiment of a camshaft lens sensor unit 01 , The difference is that the sender wheel as a gear 25 is executed, which additionally but independently of the one-piece with the camshaft 02 is constructed. The triggers are called teeth 26 educated. Furthermore, in the sensor (!) 04 two offset to each other arranged active analog sensors (!) Integrated.

The determination of the absolute position of the camshaft 02 as well as the detection of the direction of rotation of the gear 25 also takes place by means of a not shown and with the camshaft sensor unit 01 connected evaluation unit.

In 3 Fig. B) is a cross-section along the section line BB of the camshaft sensor unit 01 according to 3 , Fig. A), showing the tooth profile of the teeth 26 as well as the brand 07 on the gear 25 can be seen. The shape of the teeth 26 and the active analog sensors of the camshaft sensor unit 01 are selected so that sinusoidal sensor signals 27 . 29 (please refer 4 ) be generated.

The sensor signals 27 . 29 and the associated speed 23 of the gear 25 or the camshaft 02 are as a function of time t in the diagram of 4 shown.

Since the active analog sensors are to each other by exactly half a tooth 26 offset, resulting in a sine wave signal 27 and a cosine signal 29 , or two π / 2 offset sinusoidal sensor signals 27 and 29 , From the diagram it can be seen that when the direction of rotation of the camshaft 02 clockwise the cosine signal 29 after the sine wave signal 27 is seen. Reversing the counterclockwise rotation direction is the sine signal 27 after the cosine signal 29 to recognize. Due to the sinusoidal nature of the sensor signals 27 . 29 becomes a higher angle detection resolution or higher accuracy in the determination of the absolute position of the camshaft 02 achieved. This is especially the case when the camshaft 02 so comes to a halt that the sensor is between two teeth 26 scans.

An implementable in the evaluation unit method for determining the absolute position of the camshaft 02 when using a gear 25 as a sensor wheel and the evaluation of sinusoidal sensor signals 27 . 29 illustrates 5 ,

The diagram shows in the lower part the through the active analog single sensors of the sensor 04 out 3 , Fig. A) and b) generated sensor signals 27 and 29 and in the upper part of a possible waveform in the evaluation each as a function of time t. The signal curve in the evaluation unit represents the absolute position of the camshaft as a running angle 31 dar. The current angle 31 between the teeth 26 of the gear 25 is calculated using the arctangent function of the quotient between the sine signal 27 and the cosine signal 29 certainly. This will be the absolute position of the camshaft 02 at any time even with sensor position between the teeth 26 known at camshaft standstill.

In 6 is a cross-sectional view of a third preferred embodiment of a camshaft sensor unit 01 shown.

Instead integrated in a sensor 04 Here are the two active sensors 33 and 35 arranged and positioned separately. The sensors 33 and 35 are in the radial direction on the trigger wheel 03 directed. The sensors 33 and 35 are arranged to each other with an angular offset θ.

This figure is intended only for the arrangement of the sensors 33 . 35 illustrate. The number of trigger fingers displayed 06 corresponds to a design according to the prior art. Of course, the camshaft sensor unit 01 be included herein with the inventive number of triggers.

7 shows various views of a fourth preferred embodiment of a camshaft sensor unit 01 with one on the camshaft 02 attached magnetic pole ring 37 , The magnetic pole ring 37 Can also be one-piece with the camshaft 02 be executed.

In Fig. A) is a perspective view, in Fig. B) is a side view and in Fig. C) is a plan view of the camshaft sensor unit 01 wherein the magnetic pole ring 37 and the arrangement of the camshaft sensor unit 01 are very clearly visible.

From Fig. C) is the execution of the trigger as permanent magnets 38 with alternating polarized order of the permanent magnets 38 as well as the brand 07 on the magnetic pole ring 37 refer to. The detection of the absolute position of the camshaft 02 success here on the magnetic pole ring 37 , where the in the camshaft sensor unit 01 integrated two active sensors z. B. Hall sensors or magnetoresistive sensors.

In a suitable design of Magnetpolring 37 and selection of sensors which are familiar to the person skilled in the art can also with this arrangement sinusoidal sensor signals 27 . 29 be generated.

01

Camshaft sensor unit

02

camshaft

03

trigger wheel

04

sensor

05

06

trigger finger

07

brand

09

10

11

6-finger trigger wheel

13

sensor signal

15

sensor signal

23

rotation speed

25

gear

26

tooth

27

Sine signal

29

Cosine signal

31

ongoing angle

33

sensor

35

sensor

37

magnet pole

38

permanent magnets

QUOTES INCLUDE IN THE DESCRIPTION

This list The documents listed by the applicant have been automated generated and is solely for better information recorded by the reader. The list is not part of the German Patent or utility model application. The DPMA takes over no liability for any errors or omissions.

Cited patent literature

• WO 2005/012698 A1 [0004]
• - US 7243627 B2 [0005]
• - DE 102006017232 A1 [0006]

Claims (17)

Camshaft sensor unit ( 01 ) for determining an absolute position of a camshaft ( 02 ) at low speeds with one on the camshaft ( 02 ) attached donor wheel ( 03 . 25 . 37 ), at least one on the encoder wheel ( 03 . 25 . 37 ) directed sensor ( 04 ) and an evaluation unit, characterized in that the transmitter wheel ( 03 . 25 . 37 ) distributed on its circumference a number of triggers ( 06 . 26 . 38 ) and at least one brand ( 07 ), the number of triggers ( 06 . 26 . 38 ) determines an angle detection accuracy that is less than 20 ° NW (camshaft). Camshaft sensor unit ( 01 ) according to claim 1, characterized in that the mark ( 07 ) on an axially offset track on the sender wheel ( 03 . 25 . 37 ) is arranged. Camshaft sensor unit ( 01 ) according to claim 2, characterized in that several brands ( 07 ) are arranged on the offset track. Camshaft sensor unit ( 01 ) according to one of claims 1 to 3, characterized in that the sender wheel is a trigger wheel ( 03 ) with trigger fingers ( 06 ). Camshaft sensor unit ( 01 ) according to one of claims 1 to 3, characterized in that the sender wheel is a gear ( 25 ) with teeth ( 26 ) as a trigger. Camshaft sensor unit ( 01 ) according to one of claims 1 to 3, characterized in that the encoder wheel is a magnetic pole ring ( 37 ) with alternating polarized permanent magnets ( 38 ) as a trigger. Camshaft sensor unit ( 01 ) according to one of claims 1 to 6, characterized in that it comprises two active sensors ( 04 ), which are based on the triggers ( 06 . 26 . 38 ) of the encoder wheel ( 03 . 25 . 37 ) and are arranged with an angular offset θ to each other, whereby the of the sensors ( 04 ) generated sensor signals ( 13 . 15 . 27 . 29 ) are offset in time. Camshaft sensor unit ( 01 ) according to one of claims 1 to 7, characterized in that the shape of the trigger ( 06 . 26 . 38 ) and the sensors ( 04 ) are matched to one another such that the sensor signals ( 27 . 29 ) are sinusoidal. Camshaft sensor unit ( 01 ) according to claim 1 to 8, characterized in that the evaluation unit is a filter to improve the signal quality, the sensor signals ( 13 . 15 . 27 . 29 ). Camshaft sensor unit ( 01 ) according to one of claims 1 to 9, characterized in that the transmitter wheel ( 03 . 25 . 37 ) in one piece with the camshaft ( 02 ) is executed. Camshaft sensor unit ( 01 ) according to one of claims 7 to 10, characterized in that the sensors ( 04 ) is installed in a housing with plug or cable outlet for power supply and signals. Method for controlling an electromechanical camshaft adjuster of an internal combustion engine, for setting a desired adjustment angle of the camshaft adjuster when the internal combustion engine is started, comprising the following steps: determining an absolute position of a camshaft ( 02 at engine stop from a camshaft signal; - storing the absolute position of the camshaft ( 02 ) in a storage medium; - reading the stored absolute position of the camshaft ( 02 ) at engine start; Determining a control angle from the read position of the camshaft 02 ) and the desired adjustment angle; - Adjusting the control angle on the camshaft adjuster. A method according to claim 12, characterized in that for determining the absolute position of the camshaft ( 02 ) two, by an angle θ offset camshaft signals ( 13 . 15 . 27 . 29 ) be evaluated. Method according to claim 13, characterized in that the camshaft signals ( 27 . 29 ) are sinusoidal. Method according to claim 14, characterized in that the camshaft signals ( 27 . 29 ) are offset by π / 2 to each other and the absolute position of the camshaft ( 02 ) based on the arctangent function of the quotient between the camshaft signals ( 27 . 29 ) is determined. Method according to one of claims 13 to 15, characterized in that a determination of the order of the camshaft signals ( 13 . 15 . 27 . 29 ), by means of which a detection of a direction of rotation of the encoder wheel takes place. Method according to one of Claims 13 to 16, characterized in that control signals are generated for compensating the angular error which arises due to drive elongation and chain tensioner state on the basis of which the camshaft sensor unit ( 01 ) generated sensor signals ( 13 . 15 . 27 . 29 ) and signals generated by a similar sensor unit on the crankshaft.