WO2006048345A1

WO2006048345A1 - Method for determination of the absolute crankshaft angular position for an internal combustion engine

Info

Publication number: WO2006048345A1
Application number: PCT/EP2005/054384
Authority: WO
Inventors: Janko Bosnjak
Original assignee: Robert Bosch Gmbh
Priority date: 2004-11-03
Filing date: 2005-09-06
Publication date: 2006-05-11
Also published as: DE102004053156A1

Abstract

The invention relates to a method for determination of the absolute crankshaft angular position for an internal combustion engine, comprising a sensor disc (1), connected to a crankshaft or a camshaft in the internal combustion engine, whereby the sensor disc (1) has markings (3) made up of an alternating arrangement of teeth (4) and teeth gaps (8) and said sensor disc (1) is provided with a sensor (6), which can generate an electrical signal (Sl), which may adopt at least two signal levels (High, Low), whereby one of the signal levels (High, Low) corresponds to a tooth (4) and the other to a tooth gap (8) and the ratio of the circumferential angle of a tooth (4) to the circumferential angle of an adjacent tooth gap (8) gives a scanning ratio (TV), permitting a recognition of the absolute crank angle after only a small relative rotational angle, whereby the markings (3) have several different scanning ratios (TV) and several markings (3) in series have a unique sequence and, for determination of the absolute rotational angle of the crankshaft, the sequence of the scanning ratios (TV) is compared with a stored sequence of scanning ratios (TV).

Description

Method for determining the absolute crankshaft angle position of an internal combustion engine

The present invention relates to a method for determining the absolute crankshaft angle position of an internal combustion engine with a sensor disk, which includes a

Crankshaft or camshaft of the internal combustion engine verbun¬ is the, wherein the encoder disc has markings by alterna ¬ selnde arrangement of teeth and tooth spaces, and wherein the encoder disc is associated with a donor, which can generate an electrical signal that can assume at least two Sig¬ nalpegel, wherein one of the signal levels is associated with one tooth and the other with a tooth gap, and wherein, at the circumferential angle of a tooth to the circumferential angle of an adjacent tooth gap, a duty ratio results, as well as a sensor disc for carrying out the method.

For the control of internal combustion engines, the determination of the crankshaft position is one of the central tasks. Depending on the crankshaft angle, the injection of the fuel, the opening and closing of the intake and exhaust valves and the ignition of each cylinder are controlled in the Otto engine so that the individual working cycles run optimally.

Current solutions use incremental encoders on crank and camshafts. Customary are encoder discs with incremental markers, which enable a determination of the motor position in the interaction of the signals. From DE 10020165 Al a method for detecting the rotational speed of an internal combustion engine, on which a sensor wheel is accommodated on a rotating component, is known. The sender wheel includes a plurality of teeth scanned by speed sensors associated with the circumference of the sender wheel become. 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 un¬ known angular position (eg, when starting) so a full turn to determine the absolute angle of rotation.

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

Problems of the prior art

The determination of the absolute crankshaft or camshaft angle is currently either costly or possible by means of an absolute angle encoder. after reaching a designated mark, in the worst case after a crank or camshaft rotation.

The object of the present invention is to overcome the above-mentioned disadvantages of the prior art, in particular to enable detection of the absolute crankshaft angle after only small relative angles of rotation.

Advantages of the invention

The above-mentioned disadvantages of the prior art wer¬ avoided by a method for determining the abso¬ lute crankshaft angle position an internal combustion engine with a donor disc, which is connected to a crankshaft or camshaft of the internal combustion engine, the donor disc markings by alternating arrangement of teeth and tooth spaces, and wherein the encoder disc is associated with an encoder which generates an electrical signal. which can assume at least two signal levels, one of the signal levels being assigned to one tooth and the other to a tooth space, and the circumferential angle of a tooth to the circumferential angle of an adjacent tooth space giving a duty cycle, characterized in that the markings have a plurality of different duty cycles a plurality of successive markings have a unique sequence and that for determining the absolute angle of rotation of the crankshaft, the sequence of duty cycles is compared with a stored sequence of Tast- ratios.

The encoder disk with the previously uniformly distributed over the circumference division is here modified, namely by 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.

It is advantageous that the falling edge that is significant for engine control today continues to appear every 6 °. The fundamental signal processing can therefore be carried out unchanged, only for the absolute angle determination of the inventive signal processing is used.

The sequence of duty cycles is unique for the defined An¬ number of teeth within a revolution, ie only once available. The method according to the invention makes it possible to quickly determine the position (here after 3 teeth = 18 ° crankshaft, 36 ° camshaft). With a larger number of possible duty cycles and evaluation teeth, this can be considerably shortened (depending on the accuracy of the speed sensor, phase transmitter, encoder wheel, etc.). The position determination is at a camshaft lengeber without consideration of the crankshaft signals, ie only by the evaluation of the camshaft signals, mög¬ Lich. In addition, a better or faster diagnosis of the camshaft position and the phase encoder is possible, with a diagnosis is also possible in the start. Furthermore, an improved emergency operation with DG errors is achieved, since the smaller distance of the camshaft signals detects the speed dynamics; It may be possible to run it without restrictions on driveability. In order to carry out the method, only the encoder disk and the software are to be changed in current internal combustion engines.

In a preferred embodiment, it is provided that the markers have four different duty cycles and that three markings give a clear sequence. Depending on the accuracy of the encoder and the manufacturing accuracy of the encoder wheel, a larger number unter¬ different duty cycles can be selected here. If e.g. Distinguished eight duty cycles, it can be done after two teeth, so after 12 ° relative rotation, a detection of the absolute angle. The direction of rotation of the internal combustion engine can be determined on the basis of the direction in which the stored sequence of the pulse duty cycles is run through.

The problem mentioned at the outset is also solved by a commutator disc for a crankshaft or camshaft of an internal combustion engine, wherein the donor disc has markings by alternating arrangement of teeth and tooth gaps, and wherein the donor disc is associated with an encoder which can generate an electrical signal , which can assume at least two signal levels, wherein one of the signal levels is assigned to one tooth and the other to a tooth gap, characterized in that the markings have different pitches of the teeth to tooth gaps.

In a further embodiment of the internal combustion engine according to the invention, it is provided that it has at least three different pitches of the teeth relative to tooth gaps. drawings

Hereinafter, an embodiment of the present invention with reference to the accompanying drawings erläu¬ tert. Showing:

Figure 1 is a sketch of encoder disk and encoder.

2 shows an example of the signal curve of the transmitter in the case of an encoder disk according to the prior art (FIG. 2 a) and in the case of an encoder disk according to the invention (FIG. 2 b).

1 shows a sketch with a sensor disk 1, which is arranged, for example, directly on a crankshaft or camshaft of an internal combustion engine or indirectly connected by means of gear elements with respect to the rotation with the camshaft. The encoder disk 1 rotates about an axis 2. Markers 3 are arranged on the outer circumference of the encoder disk 1. The markings consist spielsweise of teeth 4, which are arranged over the outer circumference of the donor disc 1. Between the teeth 4 each tooth gaps 8 are arranged. Another brand 5, spielsweise as shown here in the form of a twice as wide tooth 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. A tooth and the adjacent tooth gap 8 each extend over a circumferential angle UW of approximately 6 °.

At the encoder disk 1, an encoder 6 is arranged. During a rotation of the crankshaft and thus of the encoder disk 1, the teeth 4 as well as the marking 5 are guided past the encoder 6. As a result, for example, an electrical signal is triggered in the encoder 6. The encoder 6 can Hall effect sensor, an anisotropic magnetoresistive sensor (AMR sensor), inductive or capacitive sensor or der¬ same. Alternatively, it can also work optically, for example by measuring optical changes caused by the teeth 4 or the marking 5.

Fig. 2 shows the top (Fig. 2b) the waveform of the encoder 6 over the time t at a known equidistant division. The alternating passage of teeth 4 and tooth gaps 8 produces a rectangular signal in the signal course S 1 of the transmitter 6. The signal assumes the values "High" and "Low". The transition from low to high is referred to as rising edge 11, the transition from high to low as falling edge 12. 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). The passage of the teeth 4 and tooth gaps 8 on the encoder 6 causes the transition between the two signal levels when a transition from a tooth space 8 to a tooth 4 or vice versa er¬ follows. In this case, a tooth gap 8 can be assigned a high or a low value, 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 exemplary embodiment shown here is explained on the basis of the falling flanks, but it is also possible to use the rising flanks. The distance between two falling edges is constantly 6 °. The distance between the falling flanks and the rising flanks is varied, the circumferential angle UW of a tooth to that of a following gap is thus varied. This results in different duty cycles, that is to say the ratio of the circumferential angle of a tooth 3 to the following tooth gap 8 or of a high value to the following low value, since at a known rotational speed the crankshaft wave angle in the time or relative circumferential angle in ei¬ ne time duration can be converted.

FIG. 2 shows four different duty ratios TV at the bottom (FIG. 2b). These are called TVO, TVl, 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 the associated high and low times, and therefore the sum of the duration (at constant speed as time specification, 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 uniquely defined, for example, by the length (or duration) of the high signal in relation to the distance T of two successive falling edges, which is constant at 6 ° as described above, here e.g. as TV0 = th0 / T; TVl = thl / T usf., But are also clearly defined by the ratio of successive low to high values. The following Table 1 shows an example of a possible distribution of the duty cycles on the encoder wheel 1. In the first table line is the

Tooth number, at a pitch of 6 ° results in 60 teeth 4 with associated tooth gaps 8. The duty cycles tooth / tooth gap TVl to TV4 are indicated in the second line by the numbers 1 to 4. 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-TVO) is recognized, this can be clearly assigned in Table 1 to the teeth No. 28, 29, 30. In this sequence, after the identifier has been determined and assigned to said teeth, each individual flank can be assigned to one tooth, here TV3 to tooth No. 28, TV1 to tooth No. 29, TVO to tooth No. 30. After a rotation of the sender wheel 1 by three teeth, ie 18 °, the absolute crankshaft angle is therefore exactly known to a tooth. Instead of four different duty cycles, as in the exemplary embodiment illustrated here, it is also possible, for example, to provide only three or five or more different duty cycles. This depends on the possible manufacturing accuracy of the encoder disk 1 and the accuracy of the encoder 6, since the duty cycles must be clearly recognized. For example, with only two teeth, thus after 12 ° crankshaft angle, an unambiguous recognition would have to be provided in the case of the assumed tooth pitch of 6 °, eight different duty cycles.

Tooth 1

No. 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21

TV 0 1 0 0 2 0 0 3 0 1 1 0 1 2 0 1 3 0 2 1 0

tooth

No. 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42

TV 2 2 0 2 3 0 3 1 0 3 2 0 3 3 1 1 1 2 1 1 3

Tooth no. 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

TV 1 2 2 1 2 3 1 3 2 1 3 3 2 2 2 3 2 0

The sequence of the combination ensures that this combination is present only once within one crankshaft revolution (eg from tooth no. 2, the combination 100 is present, which otherwise does not occur). The combinations are distributed so that 3 arbitrarily consecutive TV values are present only once. The sequence of the duty cycles is stored in a memory of the engine control unit. Successive rising and falling edges are each assigned to one of the duty cycles. The result is a series whose sequence is compared with the stored sequence. If three teeth have been moved past the sensor, so three duty cycles have been determined, the individual duty cycles and thus the rising / falling Flanks as previously explained clearly assigned to a tooth.

The tooth space and the tooth are modified between two negative edges in such a way that, given a constant distance between two negative edges, different ratios of gap and edge spacing result (duty cycle TV = duration gap / duration tooth spacing), eg TVO = 80%, TVI = 60%, TV2 = 40%, TV3 = 20%. From the donor wheel these TV are now angeord¬ net such that over a defined distance (here 3 teeth) a unique TV sequence is available. By comparing the TV sequence with the stored sequences, the position of the current tooth can be uniquely determined. The number of TV is chosen depending on the accuracy of the KW / NW signals. Together with the total number of teeth as well as the number of teeth to be considered, the resolution and the time necessary for determining the position result. For example, in order to be able to implement the position determination for 2 teeth with a 58-2 toothed wheel, 8 different TV's (= 64 possible combinations) are necessary. For this a resolution of 6/8 = 0.75 ⁰ KW must be possible. The direction of rotation can be done, for example, via the simultaneous evaluation of the negative and the positive edges. In the case of rotation, for example in the forward direction, the desired TV sequence results between the negative edges, and in the case of rotation in the reverse direction between the positive edges. Here, the observed range may need to be increased.

Claims

claims

1. A method for determining the absolute crankshaft angle position of an internal combustion engine having a sensor disk (1) which is connected to a crankshaft or camshaft of the internal combustion engine, wherein the encoder disk (1) markings (3) by alternating arrangement of teeth (4) and tooth spaces (8), and wherein the encoder disc (1) is associated with an encoder (6) which can generate an electrical signal (Sl) which can assume at least two signal levels (high, low), one of the signal levels (High, Low) one tooth (4) and the other 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), characterized in that the markings (3) have a plurality of different duty cycles (TV), wherein a plurality of successive markings (3) have an unambiguous sequence and that for determining the absolute rotation angle of the crankshaft di e sequence of the duty cycles (TV) with a gedicher¬ th sequence of duty cycles (TV) is compared.

2. The method according to any one of the preceding claims, characterized in that the markings (3) have four different lent duty cycles (TV).

3. The method according to any one of the preceding claims, characterized in that three markings (3) give a clear sequence.

4. The method according to any one of the preceding claims, characterized in that the direction of rotation of the internal combustion engine based on the direction in which the stored sequence of Tast¬ ratios (TV) is traversed, is determined.

5. 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 spaces (8), and wherein the encoder disc (1) is associated with an encoder (6) which can generate an electrical signal (Sl) which can assume at least two signal levels (High, Low), wherein one of the signal levels (High , Low) one tooth (4) and the other a tooth gap (8) is associated, characterized in that the markings (3) have different pitches of the teeth (4) to tooth gaps (8).

6. encoder disc according to the preceding claim, characterized in that it comprises at least three different pitches of the teeth (4) to tooth spaces (8).