DE102004053156A1 - Method for determining the absolute crankshaft angle position of an internal combustion engine - Google Patents

Abstract

In a method for determining the absolute crankshaft angle position of an internal combustion engine with a sensor disc (1) which is connected to a crankshaft or camshaft of the internal combustion engine, wherein the encoder disc (1) markings (3) by alternating arrangement of teeth (4) and tooth gaps (8 ) and wherein the encoder disc (1) is associated with an encoder (6) which can generate an electrical signal (S1) which can assume at least two signal levels (high, low), one of the signal levels (high, low) a tooth (4) and the other of a tooth gap (8) is assigned and wherein the circumferential angle of a tooth (4) to the circumferential angle of an adjacent tooth gap (8) give a duty cycle (TV), a detection of the absolute crankshaft angle is made possible after only small relative rotation angles, in that the markings (3) have a plurality of different duty cycles (TV), with a plurality of successive markings (3) being a clear succession e and that for determining the absolute angle of rotation of the crankshaft, the sequence of duty cycles (TV) with a stored sequence of duty cycles (TV) is compared.

Description

The The present invention relates to a method for the determination of absolute crankshaft angle position of an internal combustion engine with a donor disk, with a crankshaft or camshaft of the internal combustion engine connected, wherein the encoder disc marks by alternating Arrangement of teeth and tooth gaps and wherein the encoder disc is associated with a donor, the can generate an electrical signal that has at least two signal levels can assume, with one of the signal levels a tooth and the other a tooth gap is assigned and wherein the circumferential angle of a tooth to the circumferential angle an adjacent tooth gap a duty cycle give as well as a donor disk for performing the method.

For the controller of internal combustion engines is the determination of the crankshaft position one of the central tasks. Dependent from the crankshaft angle are the injection of the fuel, the opening and closing the inlet and outlet valves and the gasoline engine ignition for each Cylinder controlled so that the individual working games optimal expire.

Current solutions use incremental encoders on the crankshaft and camshaft. Common are encoder discs with incremental mark, which allow the determination of the motor position in the interaction of the signals. From the DE 10020165 A1 is a method for detecting the rotational speed of an internal combustion engine, on which a sensor wheel is accommodated on a rotating component known. The sender wheel includes a plurality of teeth that are scanned by encoders associated with the circumference of the sender wheel. The absolute crankshaft or camshaft angle can only be determined when a conventional zero mark is passed to the encoder. This marking is only once attached, in the worst case, it requires at an unknown angular position (eg when starting) so a full turn to determine the absolute angle of rotation.

From the DE 19900641 A1 a device and a method for detecting the rotation angle of the camshaft of a multi-cylinder internal combustion engine is known. To determine the camshaft angle, a permanent magnet is mounted there on the camshaft and, near the latter, a magnetic-field-sensitive sensor, through the signal of which a control unit acquires a continuous, high-resolution angle signal.

Problems of the State of the art

The Determination of the absolute crankshaft or camshaft angle is currently either expensive possible by means of an absolute angle encoder or first e.g. after reaching a designated mark, in the worst Fall after a crankshaft or camshaft revolution.

task It is the object of the present invention to overcome the aforementioned drawbacks to overcome in the prior art in particular a detection of the absolute crankshaft angle after to allow only small relative angles of rotation.

Advantages of invention

The aforementioned disadvantages of the prior art are avoided by a method for determining the absolute crankshaft angle position an internal combustion engine with a sensor disk, which is connected to a crankshaft or camshaft of the internal combustion engine is connected, wherein the Encoder disc markings by alternating arrangement of teeth and gullets and wherein the encoder disc is associated with a donor, the an electrical signal he can testify, the at least two signal levels can assume, with one of the signal levels a tooth and the other a tooth gap is assigned and wherein the circumferential angle of a tooth to the circumferential angle an adjacent tooth gap give a duty cycle, characterized in that the markings a plurality of different ones duty cycles have, wherein a plurality of successive markings a have a unique sequence and that to determine the absolute Angle of rotation of the crankshaft, the sequence of duty cycles is compared with a stored sequence of duty cycles.

The encoder disk with the previously uniformly distributed over the circumference division is modified here, namely because the division between teeth and tooth gaps is no longer uniform. The usual resolution of the angle is 6 °, with a gap of two angular units therefore 58 teeth or pole pairs are applied to the encoder disc. The pitch of the encoder disc according to the invention is no longer symmetrical with a pitch of 6 ° in 3 ° gap and 3 ° tooth, but asymmetrically, for example, with a division in 1 ° gap and 5 ° tooth, 2 ° gap and 3 ° tooth, 4th ° gap and 1 ° tooth or the like.

Advantageous is that today for the engine control relevant falling edge continues to appear every 6 °. The fundamental Signal processing can therefore be carried out unchanged, only for the absolute angle determination becomes the signal processing according to the invention used.

The Sequence of duty cycles is for the defined number of teeth uniquely within one revolution, i. only once available. The inventive method allows a quick determination of the position (here after 3 teeth = 18 ° crankshaft, 36 ° camshaft). For a larger number of possible duty cycles and evaluation teeth This can be shortened considerably be (dependent on the accuracy of the speed sensor, phase encoder, sensor wheel, etc.). The position determination is without consideration in a camshaft lengeber the crankshaft signals, i. only by evaluating the camshaft signals, possible. In addition, a better or faster diagnosis of the camshaft position and the phase encoder possible where a diagnosis is also possible in the start. Furthermore, will Improved emergency operation in the case of DG errors is achieved because of the lower Distance of the camshaft signals the speed dynamics is detected; possibly is an emergency without restrictions on drivability possible. To carry out of the method is only the encoder disk in current internal combustion engines and change the software.

In a preferred embodiment it is provided that the markers have four different duty cycles and that three markers give a clear sequence. Depending on the accuracy of the encoder and the manufacturing accuracy of the Transmitter wheel can also be a larger number of different duty cycles chosen become. If e.g. distinguished eight duty cycle, so can a recognition of the absolute angle already after two teeth, ie after 12 ° relative rotation, respectively. The direction of rotation of the internal combustion engine can be determined by the Direction in which the stored sequence of duty cycles go through will be determined.

The The problem mentioned at the beginning is also solved by a sensor disk for one Crankshaft or camshaft of an internal combustion engine, wherein the Encoder disc markings by alternating arrangement of teeth and gullets and wherein the encoder disc is associated with a donor, the can generate an electrical signal that has at least two signal levels can assume, with one of the signal levels a tooth and the other a tooth gap is assigned, characterized in that the markers different Divisions of the teeth to tooth gaps exhibit.

In a further embodiment of the internal combustion engine according to the invention provided that these have at least three different divisions the teeth to tooth gaps having.

drawings

following becomes an embodiment of the present invention with reference to the accompanying drawings. there demonstrate:

1 a sketch of encoder disk and encoder;

2 an example of the signal curve of the encoder in a prior art encoder disk ( 2a ) and in an encoder disc according to the invention ( 2 B ).

1 shows a sketch with a donor disk 1 which is arranged for example directly on a crankshaft or camshaft of an internal combustion engine or is indirectly connected by means of gear elements with respect to the rotation with the camshaft. The encoder disc 1 rotates about an axis 2 , On the outer circumference of the encoder disk 1 are marks 3 arranged. The markers consist for example of teeth 4 passing over the outer circumference of the encoder disk 1 are arranged. Between the teeth 4 are each tooth spaces 8th arranged. Another brand 5 For example, as shown here in the form of a tooth twice as wide 4 or in the form of a larger tooth spacing between two teeth 4 or the like, marks a designated zero position of the crankshaft. One tooth and the adjacent tooth gap 8th each extend over a circumferential angle UW of about 6 °.

At the encoder disk 1 is a giver 6 arranged. During a rotation of the crankshaft and thus the encoder disc 1 each become the teeth 4 as well as the mark 5 at the dealer 6 past. As a result, for example, an electrical signal in the encoder 6 triggered. The giver 6 may be a Hall effect sensor, an anisotropic magnetoresistive sensor (AMR sensor), inductive or capacitive sensor, or the like. Alternatively, this can also work optically, eg by the teeth 4 or the mark 5 caused optical changes are measured.

2 shows above ( 2 B ) the signal curve of the encoder 6 over time t at known equidistant division. The alternate passing of teeth 4 and tooth gaps 8th generated in signal path S1 of the encoder 6 a rectangular signal. The signal assumes the values "High" and "Low". The transition from low to high is considered a rising edge 11 , the transition from high to low as a descending flank 12 designated. High and Low values are the same length, namely T / 2 and result in the sum of a low and the following high value in each case 6 ° (denoted here by T). Passing the teeth 4 and tooth gaps 8th at the dealer 6 causes the transition between the two signal levels, when a transition from a tooth gap 8th on a tooth 4 or vice versa. This can be a tooth gap 8th A high or a low value is assigned, this depends on the signal generation of the encoder or the subsequent signal conditioning. For ease of understanding, in the embodiment shown here, teeth are assigned the value High, tooth gaps the value Low.

The usual pitch of 6 ° results in a total of 60 rising and falling edges. The embodiment shown here is explained with reference to the falling edges, but it can also be used the rising edges. The distance between two falling edges is constantly 6 °. The distance between the falling edges and the rising edges is varied, the circumferential angle UW of a tooth to that of a following gap is thus varied. This results in different duty cycles, ie the ratio of the circumferential angle of a tooth 3 to the following tooth gap 8th or a high value to the following low value, since at a known speed of the crankshaft angle in the time or relative circumferential angle can be converted into a period of time.

In 2 are below ( 2 B ) shown four different duty cycle TV. These are called TV0, TV1, TV2 and TV3. In each case, the lengths of the high values are shown as th0, th1, th2 and th3 and the lengths of the low values t10, t11, t12 and t13. The sum of associated high and low times, and therefore the sum of the duration (at constant speed as time, otherwise converted to the crankshaft angle) of a low value and the following high value is constant and is T or here 6 °. The duty cycles are clearly defined, for example by the length (or duration) of the high signal in relation to the distance T of two consecutive falling edges - which is constant as described above 6 °, here eg as TV0 = th0 / T; TV1 = th1 / T etc., but are also uniquely defined by the ratio of consecutive low to high values. Table 1 below shows by way of example a possible distribution of the duty cycles via the encoder wheel 1 , In the first row of the table, the tooth number is called, at a pitch of 6 ° this results in 60 teeth 4 with associated tooth gaps 8th , The contact ratios tooth / tooth gap TV1 to TV4 are in the second line with the numbers 1 to 4 designated. The tast ratios are now arranged on the encoder wheel, that three consecutive teeth give a unique, ie over the circumference of the encoder wheel occurring only once sequence. If, for example, the sequence 3-1-0 (abbreviated to TV3-TV1-TV0) is recognized, this can be clearly assigned in Table 1 to the teeth No. 28, 29, 30. In this sequence, after the identifier is detected and associated with said teeth, each individual flank can be assigned to one tooth, here TV3, tooth # 28, TV1, tooth # 29, TV0, tooth # 30. After a rotation of the sender wheel 1 by three teeth, ie 18 °, the absolute crankshaft angle is thus accurately known to a tooth.

Instead of four different duty cycles as in the embodiment shown here, for example, only three or five or more different duty cycles can be provided. This depends on the possible production accuracy of the encoder disk 1 and the accuracy of the encoder 6 from, since the duty cycles must be clearly recognized. To allow for example with only two teeth, thus after 12 ° crankshaft angle, a clear recognition would have to be provided at the imputed here tooth pitch of 6 ° eight different duty cycles.

By the sequence of the combination ensures that this combination only once within one crankshaft revolution (e.g. From tooth no. 2, the combination 100 is present, which is otherwise not occurs). The combinations are distributed so that 3 arbitrarily following TV values only once exist. The sequence of duty cycles is stored in a memory of the engine control unit. Successive Rising and falling edges are each one of the duty cycles assigned. It creates a series whose sequence with the stored Sequence is compared. If three teeth have passed the donor, So are three duty cycles has been determined the individual duty cycles and so that the rising / falling edges as previously explained clearly be assigned to a tooth.

Gap gap and Tooth are modified between two negative flanks in such a way that at a constant distance between two negative edges different circumstances from gap and edge spacing result (duty cycle TV = duration gap / duration Tooth pitch), e.g. TVO = 80%, TV1 = 60%, TV2 = 40%, TV3 = 20%. Out the transmitter wheel, these TV are now arranged such that over a defined distance (here 3 teeth) a unique TV episode is available. By comparing the TV episode with the stored Sequences, the position of the current tooth can be clearly determined become. The number of TV will depend on the accuracy of the TV KW / NW signals selected. Along with the total number of teeth as well as the number of teeth that should be considered, the resolution and the necessary time for the position determination result. For example, to determine the position of a 58-2 toothed wheel after 2 teeth to be able to implement are 8 different TV (= 64 possible Combinations) necessary. Therefor must have a resolution of 6/8 = 0.75 ° KW possible be. The direction of rotation may e.g. about the simultaneous evaluation of the negative and positive flanks take place. Upon rotation, e.g. in forward direction results between the negative flanks the desired TV episode, when turning in reverse direction between the positive flanks. Here must be the observed area may be enlarged.

Claims (6)

Method for determining the absolute crankshaft angle position of an internal combustion engine with a sensor disk ( 1 ), which is connected to a crankshaft or camshaft of the internal combustion engine, wherein the encoder disc ( 1 ) Markings ( 3 ) by alternating arrangement of teeth ( 4 ) and tooth gaps ( 8th ), and wherein the encoder disc ( 1 ) a donor ( 6 ), which can generate an electrical signal (S1) which can assume at least two signal levels (high, low), one of the signal levels (high, low) being applied to a tooth ( 4 ) and the other of a tooth gap ( 8th ) and wherein the circumferential angle of a tooth ( 4 ) to the circumferential angle of an adjacent tooth gap ( 8th ) give a duty cycle (TV), characterized in that the markings ( 3 ) have several different duty cycles (TV), wherein a plurality of successive markings ( 3 ) have a unique sequence and that for determining the absolute angle of rotation of the crankshaft, the sequence of duty cycles (TV) with a stored sequence of duty cycles (TV) is compared. Method according to one of the preceding claims, characterized in that the markings ( 3 ) have four different duty cycles (TV). Method according to one of the preceding claims, characterized in that three markings ( 3 ) give a clear sequence. Method according to one of the preceding claims, characterized characterized in that the direction of rotation of the internal combustion engine based the direction in which the stored sequence of duty cycles (TV) is determined. Encoder disc ( 1 ) for a crankshaft or camshaft of an internal combustion engine, wherein the encoder disc ( 1 ) Markings ( 3 ) by alternating arrangement of teeth ( 4 ) and tooth gaps ( 8th ), and wherein the encoder disc ( 1 ) a donor ( 6 ), which can generate an electrical signal (S1) which can assume at least two signal levels (high, low), one of the signal levels (high, low) being applied to a tooth ( 4 ) and the other of a tooth gap ( 8th ), characterized in that the markings ( 3 ) different pitches of the teeth ( 4 ) to tooth gaps ( 8th ) exhibit. Encoder disc according to the preceding claim, characterized in that it has at least three different pitches of the teeth ( 4 ) to tooth gaps ( 8th ) having.