DE19638338A1 - Encoder arrangement for quick cylinder recognition in an internal combustion engine - Google Patents

Description

The invention relates to an encoder arrangement for fast Cylinder detection in a multi-cylinder Internal combustion engine according to the type of the main claim.

State of the art

So with a multi-cylinder internal combustion engine cylinder-specific regulation can be done, it is required that in the control unit of the internal combustion engine the exact position of the crankshaft and camshaft is known, which also means the position of the individual cylinders is known. It is usually provided for this purpose To use crankshaft sensors and a camshaft sensor, these sensors with the crankshaft and the camshaft connected encoder disks with a characteristic Scan the surface and output signals to the control unit deliver that carries out the required evaluations and Trigger pulses triggered.  

So as soon as possible after the start Information regarding the position of the crank and the Camshaft can be obtained is in the published patent application DE-OS 42 43 177 proposed in a device for rapid cylinder detection in an internal combustion engine the crankshaft to attach a sender disc, the one Has a plurality of similar angle marks and at least a reference mark by two missing angle marks is formed. On the by the crankshaft Internal combustion engine driven camshaft is a second Encoder disk attached to the surface of one on the Number of cylinders of the internal combustion engine matched number of Has angle marks. These angle marks are like this designed that they are distinguishable from each other.

The two encoder disks are more suitable with the help Sensor scanned. The output signals of these sensors are evaluated in the control unit and when generating Ignition and injection pulses taken into account.

Advantages of the invention

The encoder arrangement according to the invention for fast Has cylinder detection in an internal combustion engine the known device has the advantage that one more faster and more reliable cylinder detection can be carried out at the start. Because of the advantageous Design of the encoder disks or the associated ones Angle marks are different types of systems can be used, for example inductive sensors, Hall sensors, capacitive sensors or with a corresponding modification also optical sensors.  

This advantage is achieved by using the crankshaft the encoder disk connected to the internal combustion engine has two reference marks that are opposite each other or by using a number of fiducials, which corresponds to the number of cylinders in the internal combustion engine. The connected to the camshaft of the internal combustion engine Encoder disc has a so-called segment angle mark pro Number of cylinders Z, the distances between the segment Win kel brands are the same. Z is minus 1 segment angle marks each assigned a synchronization angle mark, where the distances between the segment angle marks and the associated synchronization angle marks different are. By scanning the angle marks using a suitable Characteristic pulse trains are generated, the be evaluated in the control unit.

Further advantages of the invention are shown in the Characteristics specified achieved. It is particularly advantageous that plausibility studies can run, which show if that Output signal of a transducer is faulty. To do this Time intervals between successive signals measured and compared. With implausible Comparison results are concluded on an error. If a signal is recognized as correct, Implement an emergency run based on this signal. The at Accelerating or decelerating problems during the plausibility check fix advantageously by the Plausibility studies based on the quotient of a  previous time interval with the current time interval between predeterminable pulses.

By evaluating the after synchronization expected sequence of through synchronization angle marks caused sync pulses with actually registered Synchronizing pulses can be a possibly occurring Error in that assigned to the camshaft sender disc Recognize transducers.

The encoder arrangement according to the invention for fast Cylinder detection in a multi-cylinder Internal combustion engine can both advantageously for diesel and also spark-ignited internal combustion engines deploy. In diesel engines with EDC systems the injection can be based on that of the claimed Signals delivered after very early on the start of the internal combustion engine and also in the further Regulate the course of operation of the internal combustion engine.

drawing

The invention is illustrated in the drawing and is in the following description explained. In detail shows

Fig. 1 shows an embodiment of the invention for a four-cylinder internal combustion engine with the two encoder disks and the control unit.

In FIG. 2, the relationship between the surface of the transducer disks, and the signals generated is illustrated.

Fig. 3 shows prepared waveforms of the output signals of the two sensors and

Fig. 4 shows the sequence of the camshaft synchronization and segment angle mark signals.

In Fig. 5, an overall representation of the quick start Ge serscheen configuration for a four-cylinder internal combustion engine is plotted over the crankshaft angle, the area extending over more than one working cycle, that is to say more than 720 ° KW.

FIGS. 6, 7 and 8 show the corresponding transducer disks, and waveforms in an internal combustion engine having 3 cylinders.

description

In Fig. 1 an embodiment of the invention is shown schematically, wherein only the parts essential to the invention are specified by the internal combustion engine. In particular, FIG. 1 shows a rigid with the crankshaft 10 connected to encoder pulley 11 having a number of identical angle marks on its circumference 12 has. The angle marks 12 extend over a length L1 and are at a distance L2 from one another. Two reference marks 13 , 14 are formed by two missing angle marks. They face each other on the encoder disc. The length L1 of the angle marks is in the correct ratio, e.g. B. to choose the pole core of the associated transducer.

A second encoder disk 15 is connected to the camshaft 16 of the internal combustion engine and has segment angle marks 17 on its circumference, with a length L3. In a four-cylinder internal combustion engine, there are four segment win marks, which are each arranged at the same distance from one another. In addition to the segment angle marks 17 a, 17 b, 17 c, 17 d, there are further synchronization angle marks 18 a, 18 b, 18 c, one of the synchronization angle marks being assigned to a segment angle mark and the distances between the segments - Angle marks and the synchronization angle marks are of different lengths. One of the segment angle marks, in the exemplary embodiment of the segment angle mark 17 d, is not assigned a synchronization angle mark.

The camshaft 16 of the internal combustion engine is driven in a conventional manner by the crankshaft 10 and rotates at half the speed of the crankshaft 10 . The rigid connection between crankshaft 10 and camshaft 16 is symbolized by line 19. When the shafts and thus the encoder disks rotate, the angle marks run past the sensors 20 and 21 . Tensions are generated in the transducers that reflect the surface of the encoder disks. The encoder disk 11 and the sensor 20 are also referred to as crankshaft sensors and the sensor disk 15 with the sensor 21 as a camshaft sensor.

Inductive sensors, Hall sensors, capacitive sensors or, with a corresponding adaptation, also optical sensors can be used as sensors, these optical sensors then consisting of a transmitter and a receiver and angular marks moving between these two elements. The direction of rotation of the shafts or disks is indicated by an arrow. The signals from the pickups 20 and 21 are designated S1 and S2. They are fed to a control unit 22 in which at least one computing device, for example a microprocessor including the associated memory, is present. The signal curves are evaluated in the control unit.

In the control unit, for example in the case of a diesel internal combustion engine, an EDC control unit, the calculations required for controlling the internal combustion engine are carried out on the basis of the signals S1 and S2 supplied by the sensors 20 , 21 . For this purpose, the control device is supplied with further information, which is supplied by corresponding sensors and is supplied via corresponding inputs E1. From the starter switch 23 , the information that the internal combustion engine is to be started is sent to the control unit 22 via the input E2. The control unit, for example, sends injection pulses to the injection valves 24 via outputs A1. The voltage is supplied via the switch 25 by the battery 26 .

The embodiment shown in Fig. 1 in which the cylinder top positions for an ignition sequence 1-3-4-2 are given as an example, is to be used, for example, in connection with an electronically controlled single-pump diesel injection system in which the assignment the injectors are electronic. This requires cylinder detection for synchronization. When starting, the injection should take place at the next but one ignition top dead center (top dead center). Such a rapid injection is called a quick start. In order to be able to implement the quick start, a two-gap sensor disk 11 is mounted on the crankshaft 10 in a four-cylinder internal combustion engine, for example with 60 minus 2 times 2 angle marks. A sensor disk 15 is connected to the camshaft 16 , for example 4 times 2 minus 1 angle marks 17 a to d, 18 a to c. Each cylinder of the internal combustion engine is assigned a so-called segment angle mark on the encoder disk 15 assigned to the camshaft 16 . Three of the four cylinders each additionally receive a synchronization angle mark arranged at a characteristic distance from the segment angle mark. No synchronization angle mark is placed on one of the cylinders, only a segment angle mark. From the defined mounting position of the encoder disks relative to one another, a specific crankshaft encoder disk angular label 12 can be assigned to each segment or synchronization angle label. This enables clear cylinder recognition and thus synchronization of the crankshaft encoder disk.

As a boundary condition for the design of the The following relationships were exemplary embodiments considered:

• 1. After the internal combustion engine has come to a standstill, usually one Preferred location (VZL). This preferred location is due to the design around 90 ° +/- 15 ° KW (crankshaft angle) before TDC.
• 2. If inductive sensors are used as transducers Signals can only be evaluated from approx. 50 revolutions per minute receive. Passes by as the starter accelerates thus until the minimum speed is reached, from which a Inductive sensor emits a usable output signal certain crankshaft angle segment, which is why in the A lead must be scheduled for cylinder detection. It will  however, provided that this lead is less than 60 ° KW is.
• 3. The first period of the output signal of the Transducer, which is connected to the crankshaft Scanning the encoder disc can only be recognized when at least two pulses of the signal were evaluated.
• 4. Before the first injection can take place, the angle clock, which is, for example, a 16-bit counter that supplies the current crankshaft angle and controls the course of the injection, is first synchronized with the crankshaft angle. For this, at least one reference mark 13 or 14 of the crankshaft must be exceeded. At the first flank of the angle mark after the reference mark has expired, the angle clock starts counting.
• 5. After the synchronization of the angle clock, the Evaluation of the signals associated with the camshaft Sensor to identify the correct cylinder.
• 6. The earliest start of funding is 20 ° KW before OT.
• 7. The earliest start of funding at speeds greater than 3500 Revolutions per minute is 20 ° KW before TDC.
• 8. The latest injection end is 30 ° KW after TDC.
• 9. When choosing the location of the reference marks, demands must be met due to the smooth running regulation (LRR) and anti-juddering (ARD). In the  Smooth running control and anti-jerk damping are concerned to procedures known from the EDC.

Taking into account the boundary conditions 1 to 9 and the configurations of the encoder disks shown in FIG. 1, including the angular distributions given by way of example, the signal curves shown in FIGS . 2 and 3 or relationships between signals and the encoder disk surface result. In FIG. 2, the example of the camshaft segment of cylinder 2 shows how the signals are generated. Here, in Fig. 2a c show the surface of the donor wafer 15 in the region of the segment mark 17, and the synchronization Win kelmarke 18 shown c. The distance between the segment angle mark 17 b and the synchronization angle mark 18 b is 18 ° NW (that is, based on the camshaft). The direction of rotation is symbolized by an arrow. In Fig. 2b is the corresponding waveform S2, which the pickup 21 supplies represented. The square-wave signal shown in FIG. 2c, which is ultimately used for synchronization, is formed from this signal curve.

In Fig. 2d the surface of the encoder disk 11 is shown, with the angular points 12 and the reference mark 14. In the sensor 20 , the signal S1 is generated that is indicated in Fig. 2e. The rectangular signal, which is shown in FIG. 2f, is formed from this signal S1. Square wave signals are formed from sinusoidal signals in a generally known manner. It can take place, for example, in an evaluation circuit assigned to the transducer or in control unit 22 .

In Fig. 3, the processed signals are applied over the crank angle, the crank angle in degrees OT is given. In Fig. 3a, the so-called incremental signal obtained from the scanning of the plurality of angle marks on the crankshaft sensor disk, which results when using a crankshaft sensor disk 11 according to Fig. 1, is shown. This increment signal is at the input of the angle clock integrated in the control unit. In Fig. 3b, the processed camshaft sensor signal, which is present at the input of the computer of the control unit 22 for the different areas of the camshaft Ge assigned to the respective cylinders is shown. In Fig. 3c it is shown in which crankshaft angle tolerance range the camshaft Ge transmission signals may occur so that they can still be clearly assigned.

Because of boundary conditions 1 and 4 , the reference mark lies between the preferred position of the internal combustion engine and the next but one ignition TDC. Through a suitable installation, the reference mark is located directly behind the latest possible angle at which the solenoid valve is open. There is therefore a sufficiently large crankshaft angle range for cylinder detection.

As can be seen from Fig. 3, the maximum total tolerance of the position of the camshaft pulses to the crankshaft pulses must be less than +/- 9 ° KW. This overall tolerance is made up of the manufacturing tolerances of the angle marks and the mounting tolerances of the two encoder disks, the angle of rotation between crankshaft 10 and camshaft 16 and inaccuracies in signal acquisition and the processing time of the computer.

The crankshaft sensor signal can be checked for plausibility if the crankshaft and camshaft sensor signals are intact in order to identify the functionality of the sensors or the subsequent conditioning circuits. This plausibility check is carried out by evaluating the camshaft sensor signal. For this purpose, the period between two successive segment signals is measured. When using a quick start camshaft encoder disk with variable angular mark spacings for the cylinder coding , the method explained below with reference to FIG. 4 can be used to reliably distinguish between segment angular mark and synchronization angular mark and can be used to recognize a specific cylinder segment.

In FIG. 4, the sequence of the camshaft sensor signals is shown. A specific segment angle mark or synchronization angle mark can be recognized by continuously forming the quotient Qn of the preceding period Tn-1 with the current period Tn. The quotient thus becomes:

educated. If accelerations or decelerations occur, the period duration quotient deviates considerably from the value at steady-state speed and it can happen that different period duration quotients take on the same value and therefore successive camshaft angle mark distances must be chosen so that the associated period duration quotients are as far apart as possible. In addition, you should continuously check whether the sequence of the period ratios corresponds to the specified sequence. Only then is it possible to clearly assign a certain quotient to the associated camshaft angle mark. This requirement results in the optimal arrangement of the synchronization angle marks in FIG. 4.

The fluctuation of the period quotient by the accelerations actually occurring, or Delays in the start, i.e. in a phase in which an acceleration due to the low instantaneous speeds particularly strong effects and during normal operation can be checked on the engine test bench.

A further plausibility check can be explained as follows using the relationships shown in FIG. 5. FIG. 5 shows the encoder disk configurations or signals already shown with reference to FIG. 2, over a larger crankshaft angle range. The associated system of a quick start encoder disk configuration for a four-cylinder internal combustion engine is able to quickly recognize the current cylinder by means of synchronization angle marks on the camshaft encoder disk. This is realized by querying the position of the synchronization angle mark to be checked in the cylinder segment. If a position is identified from several possible positions, then this position, defined by an upper and a lower limit, is assigned to a cylinder in the data record which is stored in the computer of the control device. If a cylinder is identified, a cylinder counter then runs. This cylinder counter runs from zero to three in a four-cylinder internal combustion engine. In general, Z cylinders are counted up to Z-1. By checking the correctness of this process, further information regarding the functionality of the system can be obtained. To determine whether the process is correct, the position of the synchronization angle marks is checked in reverse order. The determined counter reading indicates a specific position of the synchronization angle mark, which is stored in the data record. If the angle mark that occurs has this target position, it is classified as plausible. If it has a different position than the position determined by the cylinder counter and defined with a lower and upper limit position in the data record, the relevant synchronization angle mark is classified as faulty and, if necessary, a malfunction of the system is recognized and displayed.

In FIGS. 6, 7 and 8, the crankshaft Ge are berscheibe indicated the camshaft sensor disc, and the associated waveforms for a 3-cylinder internal combustion engine. The encoder disk connected to the crankshaft has a reference mark for each cylinder.

Claims (10)

1.Sensor arrangement for fast cylinder recognition in an internal combustion engine with Z-cylinders, with a sensor disk driven by the crankshaft with a plurality of similar angle marks and at least one reference mark assigned to a fixed crankshaft angle, with a sensor disk driven by the camshaft with one of which Number of cylinders Z dependent number of similar segment angle marks, with sensors that scan the angle marks and deliver corresponding signals to the control unit of the internal combustion engine, characterized in that the number of reference marks on the encoder disk driven by the crankshaft is Z / 2 or Z and that on the encoder disk connected to the camshaft, additional Z-1 synchronization win mark marks are available, each of which is assigned to the segment angle mark with different angular spacing, with no segment angle mark being assigned to a segment angle mark. 2. Encoder arrangement according to claim 1, characterized in that the segment angle marks and the synchronization win kel brands are the same size. 3. Encoder arrangement according to claim 1 or 2, characterized characterized in that the transducers inductive sensors or Hall sensors or capacitive sensors or optical sensors are, the design of the encoder disks and Selection of the material of the encoder disks according to the sensors used. 4. Encoder arrangement according to one of the preceding claims, characterized in that the encoder disc ( 11 ) with the crankshaft ( 10 ) and the encoder disc ( 15 ) with the camshaft ( 16 ) are assembled so that during operation of the internal combustion engine and the rotation that occurs the encoder disks in the sensors ( 20 , 21 ) signals are generated in such a way that each angle mark signal from the camshaft encoder disk can be assigned a specific counter reading from the signal from the crankshaft encoder disk, which enables clear cylinder detection. 5. Encoder arrangement according to one of the preceding claims, characterized in that after Cylinder identification is checked whether the next expected cylinder identification actually occurs and if this is not the case, a malfunction is detected. 6. Encoder arrangement according to claim 6, characterized in that that the cylinder identification by evaluating the Distance between one segment mark and the following Synchronization mark is done.   7. Encoder arrangement according to one of the preceding claims, characterized in that during certain Operating states or during predefinable times Plausibility studies run, which are the sequence of Pulses from the crankshaft and camshaft sensor signals evaluate and if there is a deviation from the expected Sequence an error is displayed. 8. Encoder arrangement according to claim 7, characterized in that that the plausibility check by evaluating the Quotients of the previous period Tn-1 and current period Tn takes place, whereby a Differentiation between segment and synchronization win kel brand is possible. 9. Encoder arrangement according to one of the preceding claims, characterized in that after the cylinder identification a cylinder counter is started that runs from 0 to Z-1, that from the meter reading to the position of a definable Synchronization angle mark is closed and on Plausibility is recognized when the location of the expected Corresponds to the angle mark. 10. Encoder arrangement according to claim 9, characterized in that that plausibility is also recognized if a Deviation lies within predefined limits.