DE102004061808A1 - Combustion engine control procedure has two toothed, magnetic or optically marked discs with comparison of sensor output with time average pulse length - Google Patents

Abstract

A combustion engine control procedure has two toothed, magnetic or optically marked discs producing high and low electrical output signals used to create a time average pulse length for comparison with the sensor output to determine the crank shaft rotation direction. Independent claims are included for an engine control unit using the procedure.

Description

The The present invention relates to a method of operating an internal combustion engine with a donor disk, with a crankshaft of the internal combustion engine coupled, wherein the encoder disc a mark by alternating Arrangement of teeth and tooth gaps and wherein the encoder disc is a first encoder and a second encoders are assigned, each having an electrical signal can produce that can assume at least two signal levels, one of the signal levels one tooth and the other is associated with a tooth gap, wherein the Furthermore, for determining the direction of rotation and increment of the angle of rotation the crankshaft each a rising or falling signal edge one signal and the signal level of the other signal used is and where of both electrical signals is a pulse length coded Encoder signal is generated, whose period is equal to those of the signals the encoder is and its pulse length encoded the direction of rotation of the crankshaft and a control device for carrying out the Process.

For the controller of internal combustion engines is the determination of the crankshaft angle one of the central tasks. Known solutions use incremental Encoder on crankshaft and camshaft. Common are encoder discs with Incremental marks, in the interaction of the signals of crankshaft and Camshaft allow a determination of the motor position.

For the others Improvement of the engine control arises the requirement, the crankshaft position at Parking the engine accurately detect. This makes it possible for the Reboot the engine significantly to accelerate, with positive Effect on comfort and exhaust emissions. When engine shutdown can but a hunting of the engine occur, i. an alternating movement in both directions until it stops. The currently used Donors can do not recognize the direction of rotation and thus are not able to the absolute position reliable to determine.

A Extension of the crank angle encoder by a direction of rotation detection is possible in principle. To At least two sensor elements in the encoder housing are suitable to arrange. Out the temporal relationship of the two sensor signals can then Direction of rotation can be determined. Encoder without direction of rotation detection have an output, i. a total of three connections (supply voltage, ground, Signal output). Encoders with direction of rotation detection often contain two Outputs. In one execution the signals of the two sensor elements are led out, in another version are an exit for the tooth frequency information and another output for the direction information intended. It has already been proposed, a signal coding to choose, transmits the tooth frequency and direction of rotation via just one connection. The Signal coding should be done by the pulse length of the signal. For example, means a first pulse length Clockwise rotation and another pulse length left turn.

Problems of the State of the art

Problematic Signal coding in the prior art is the unique recognition the respective coding for each Direction of rotation and monitoring the encoder for correct function. Object of the present invention it is therefore an improved recognition of differently coded To ensure signals and possibly to allow for error correction.

Advantages of invention

The aforementioned disadvantages of the prior art are solved by a method for operating an internal combustion engine with a sensor disk, which is coupled to a crankshaft of the internal combustion engine, wherein the encoder disc a mark by alternating arrangement of teeth and tooth gaps and wherein the encoder disc is a first encoder and a second encoders are assigned, each having an electrical signal can generate which can assume at least two signal levels, one of the signal levels one tooth and the other is associated with a tooth gap, wherein the Furthermore, for determining the direction of rotation and increment of the angle of rotation the crankshaft each a rising or falling signal edge one signal and the signal level of the other signal used is and where of both electrical signals is a pulse length coded Encoder signal is generated, whose period is equal to those of the signals the encoder is and its pulse length encoded the direction of rotation of the crankshaft, wherein from the pulse length coded Encoder signal a mean pulse length is formed and the pulse length the encoder signal for determining the direction of rotation of the crankshaft with the mean pulse length is compared.

Under Tooth and tooth space Here too, the alternate arrangement of markings, e.g. understood by magnetic or optical marks. The pulse length is the time while the signal level is low or high. It is preferably provided that when the signal level of one of the encoders changes, the signal level the other encoder is determined and a mapping table the Direction of rotation of the crankshaft is removed. Preferably, the Further provided that when changing the signal level of a the encoder in the control unit a counter for the Crankshaft angle dependent is incremented or decremented by the direction of rotation. Of the Comparison of the pulse length the encoder signal provides a statement as to whether the pulse length is greater than or equal to less than the mean pulse length is. Are more than two pulse lengths coded, e.g. for additional transmission of operating status information, so here are several comparisons in parallel or in succession.

In a development of the method is provided that the middle pulse length an average over the Time is. The mean value is for a (relatively short) past Period formed for example by a low-pass filter.

Preferably is the mean value of the pulse length a threshold value for the assignment of the pulse length of the pulse-length-coded Encoder signal to a direction of rotation. Is the current pulse length greater than the threshold, so the one direction of rotation is detected, this is smaller, the other direction of rotation is detected.

Of the Threshold is preferably made from a constant ratio of Pulse lengths, preferably according to S = (K + 1) / (2 · K) · PL_fil, determined. The relationship both pulse lengths is at usual Circuits constant, although the individual pulse lengths, e.g. change with the temperature can.

The The above problem is also solved by a method for Operation of an internal combustion engine with a sensor disc, with a crankshaft of the internal combustion engine is coupled, wherein the Encoder disc a mark by alternating arrangement of teeth and gullets and wherein the encoder disc is a first encoder and a are assigned second encoder, each generating an electrical signal can, which can assume at least two signal levels, one of the signal levels one tooth and the other is associated with a tooth gap, wherein the Furthermore, for determining the direction of rotation and increment of the angle of rotation the crankshaft each a rising or falling signal edge one signal and the signal level of the other signal used is and where of both electrical signals is a pulse length coded Encoder signal is generated, whose period is equal to those of the signals the encoder is and its pulse length encodes the direction of rotation of the crankshaft, wherein a counter increments the crankshaft angle or decremented, where the state of the counter when reaching the zero mark on the sender wheel with the actual Crankshaft angle is compared. The counter reading deviates from that by the zero mark clearly definable crankshaft angle from, so is an error bit set.

The The aforementioned problem is also solved by an internal combustion engine with a donor disk, with a crankshaft of the internal combustion engine coupled, wherein the encoder disc a mark by alternating Arrangement of teeth and tooth gaps and wherein the encoder disc is a first encoder and a second encoders are assigned, each having an electrical signal can produce that can assume at least two signal levels, one of the signal levels a tooth and the other is associated with a tooth gap, wherein the Furthermore, for determining the direction of rotation and increment of the angle of rotation the crankshaft each a rising or falling signal edge one signal and the signal level of the other signal used is and where of both electrical signals is a pulse length coded Encoder signal is generated, whose period is equal to those of the signals the encoder is and its pulse length the direction of rotation of the crankshaft encoded at which a threshold from the pulse length coded Encoder signal is formed and the threshold and the unfiltered pulse-length encoded Encoder signal is connected to a comparator.

The pulse-length encoded Encoder signal for thresholding is preferably initially with filtered a low pass. The filtered signal is then preferably an amplifier supplied which forms the threshold.

The The problem mentioned at the outset is further solved by the control unit for an internal combustion engine according to the invention, this is a method according to the invention To run can.

drawings

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

1 a sketch of donor disk and donors;

2 a first example of the signal waveform of the encoder;

three the representation of the pulse length coded signals for both directions of rotation;

4 a block diagram for monitoring the crankshaft angle encoder;

5 a circuit diagram for implementing the method according to the invention.

1 shows a sketch with a donor disk 1 which is arranged for example directly on a crankshaft or camshaft 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 three arranged. The markers consist for example of teeth 4 , each equidistant 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 (zero mark). The teeth each extend over an angle of about 3 °, the tooth gaps over an angle of 3 °. A tooth 4 as well as the adjacent tooth gap 8th thus extend over an angle of about 6 °.

At the encoder disk 1 are a first donor 6 and a second donor 7 arranged. The givers 6 . 7 are in the different angular ranges over the encoder disc 1 distributed. Both donors are preferred 6 . 7 arranged in a common housing. In this case, they can be arranged at a (small) angle α, which is for example about 1 to 15 ° to each other. A particularly advantageous solution is a sensor with at least two sensor elements located in close proximity. An embodiment is the integration of at least two Hall elements on egg nem IC at a distance of a few millimeters, the IC also contains the evaluation circuit. The two Hall elements then correspond to the donors 6 and 7 , And the evaluation circuit determines the direction of rotation from the temporal reference of the encoder signals and generates as an output the pulses described. The design of the known crankshaft encoder can then be maintained and allows a transition to this encoder without major system adjustments to the engine.

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 donors 6 . 7 past. As a result, for example, an electrical signal in the donors 6 . 7 triggered. The givers 6 . 7 can be inductive or capacitive sensors. Alternatively, the donors 6 . 7 also work optically, eg by bringing these through the teeth 4 or the mark 5 to be able to measure optical changes induced in it.

2 shows the signal curve of the encoder 6 . 7 over time t. The alternate passing of teeth 4 and tooth gaps 8th generated both in the waveform S1 of the first encoder 6 as well as the signal curve S2 of the second encoder 7 each a rectangular signal. Both signals assume 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.

The rising edge 11 is in the following Tables 1 and 2 with "L → H", the descending edge 12 with "H → L" DR denotes the direction of rotation of the crankshaft, with → the crankshaft anti-clockwise, and ← the right-hand rotation.

During the rising or falling edge of the signals S1 and S2 can be off the then constant each other signal are determined in which direction the crankshaft is turning. If, for example, the flank falls the signal S1 (H → L) and if the signal S2 is at the high level, the crankshaft rotates left around.

The usual resolution of the angle is 6 ° and with a gap of 2 angular units 58 tooth or pole pairs are applied to the encoder wheel. The sensors 6 . 7 are now mounted so that the angle between them is larger than the gap in the sender wheel. Thus, one of the two encoders always detects the movement of the crankshaft. The angle α is to be chosen so that this no direct multiple of the pitch of the encoder disc 1 represents, then the signals of the two sensors 6 . 7 each clock would be equal without a phase shift.

In order to enable a direct evaluation of the direction of rotation by means of a signal for the engine control unit, an according to three coded signal generated. The signal curve Z of one of the encoders is shown 6 . 7 over time and two different signals PL1 and PL2 derived therefrom over time. The first as a square wave signal of one of the donors 6 . 7 supplied signal Z is based on the table 1 or 2 in a pulse length coded encoder signal (PL) with direction information according to three transformed. In the example of three shows a signal PL1 with a defined longer high level, for example, the clockwise, a signal PL2 with a defined shorter high level to the reverse rotation of the crankshaft. The rising edges are also temporally (and thus related to the crankshaft angle) identical to the signal of one of the donors, 6 . 7 and serve to increment or decrement a counter for the crankshaft angle in the control unit.

The pulse length is in the example shown as the time of the signal at a high level understand. The assignments are of course also to the other tooth flank possible, as can the pulse length also be defined as time at low signal level. The period the encoder signal is still equal to the period of the tooth signal, only the pulse length is a variable of the direction of rotation. It is additionally possible to have one or more additional ones pulse lengths PL (i), e.g. detected error conditions or information about changes in the Transmit ambient conditions.

It In the following two methods are explained, which are monitoring such a crankshaft encoder and the adaptation of the signal evaluation for the Enable interface from encoder to evaluation unit.

This in 4 The block diagram is a monitoring of the encoder in the motor controller and detects whether the direction of rotation detection in the encoder works correctly. Shown are the signal Z and the two according to three pulse length coded signals PL1 and PL2. During normal engine operation, only one direction of rotation is observed on the crankshaft, this signal can be plausibility checked in a known manner. The number of pulses per revolution corresponds to a number of teeth of the encoder wheel (usually 60 - 2 = 58). For the correct detection of the opposite direction of rotation, the motor run-out and the subsequent motor standstill must be included. A suitable operating mode is start-stop operation, the engine is shut down by the engine control, but the transmitter and engine control continue to operate during this phase to restart the engine.

The additional direction of rotation information is used in a suitable counter Z in the engine control to determine the exact crankshaft angle. The counter reading is increased by 6 ° when one direction of rotation is detected (with a 60 - 2 encoder wheel), this is Z + 6 in 4 shown and reduced at the other direction of rotation by 6 °. This is with Z - 6 in 4 designated. In the case of a reversal of the direction of rotation, an increment of 3 ° is used once to take into account the shift of the falling edge. The counter Z must be synchronized at least once after starting the engine on the crankshaft that can, as in existing systems after detecting the gap in the sensor wheel signal, in 4 as 360 °? designated, done. From the counter Z and the detection of the 360 ° mark, the absolute crankshaft angle KW abs can now be determined.

The counter content is now always checked when reaching an excellent position of the encoder wheel, eg after passing the gap in the sender wheel. Irrespective of the number of forward and reverse rotations, the counter content must be 0 ° or 360 ° over one revolution of the crankshaft. If the counter value deviates from these values, the counter is forcibly set to 0 ° and an entry is set in a memory for error states. In start-stop mode, the engine stops permanently and the corresponding crank angle is stored in the counter. If the engine is restarted, eg by switching on the star ters, the counter continues to run with each pulse. At the latest after one crankshaft revolution, the gap is traversed and a test of the counter content is carried out.

The second method shown below according to 5 allows the signal evaluation to be adapted to changes in the crankshaft encoder. The encoder signal PL is pulse-length-coded as described. The pulse lengths PL1 and PL2 are derived from a system clock in an electronic circuit in the encoder and are in a defined ratio: K = PL1 / PL2

Of the System clock and thus the pulse lengths hang from various parameters, e.g. Temperature, supply voltage, Tolerances of the circuit components. There will be several 10% deviation specified, here is not the accuracy of a quartz-controlled Takts to be expected. The factor K is fixed, however, since the pulses pass through digital circuit parts derived from a single clock signal become. The following procedure takes into account the measured pulse length and adapts the signal evaluation.

In the control unit must be reliably distinguished between the two pulse lengths to calculate the crank angle correctly. In order to increase the immunity to interference of the encoder signal, the pulse width PL1 is continuously measured in the control unit in fired engine operation and filtered with a low-pass filter TP. The method according to the invention is enabled by a signal FG generated in the fired mode. The output signal PL_fil of the low-pass filter TP is then an average of the pulse length over a certain time and thus also follows slow changes in the pulse length, for example due to temperature changes in the encoder. The threshold for distinguishing the pulse lengths PL1 and PL2 is now adjusted so that they always the value S = (K + 1) / (2 · K) · PL_fil equivalent. The factor S is a fixed quantity with respect to the value K for the encoder, therefore the correction term (K + 1) / (2 * K) is to be set only once in the control unit as a parameter. Thus, the threshold is optimally in the middle between the two pulse lengths. 5 describes the calculation. The threshold value S is obtained by multiplying the mean pulse length PL_fil and the term (K + 1) / (2 · K). The pulse length PL of each pulse is compared with S. If S is greater than the pulse length PL, it is decided to PL2 and thus anticlockwise. The counter for the crankshaft angle is changed by one increment (eg + 6 °). If S is smaller than the pulse length PL, it is decided to PL1 and thus clockwise. The counter for the crankshaft angle is changed by one increment (eg -6 °).

For a coding the pulse lengths PL1 and PL2, where the factor K is less than one, changes Assignment of the comparison with S. If S is greater than the pulse length PL, is decided on PL1 and thus clockwise. The counter for the crankshaft angle is increased by one increment (e.g., + 6 °) changed. If S is smaller than the pulse length PL, is decided on PL2 and thus anticlockwise. The counter for the crankshaft angle is then changed by one increment (e.g., -6 °).

The method described can also be used if, for example, for the detection of diagnostic conditions or the like. further pulse lengths PL (i) with the relationship K (i) = PL1 / PL (i) generated by the encoder. Then, a threshold S (i) can be determined as described.

In an extension, both methods are also for a donor to the camshaft usable if its signal is coded as described.

Claims (10)

Method for operating an internal combustion engine with a sensor disk ( 1 ), which is coupled to a crankshaft of the internal combustion engine, wherein the encoder disc ( 1 ) a mark ( three ) by alternating arrangement of teeth ( 4 ) and tooth gaps ( 8th ), and wherein the encoder disc ( 1 ) a first donor ( 6 ) as well as a second donor ( 7 ), each of which can generate an electrical signal (S1, S2) 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 In addition, for determining the direction of rotation and increment of the angle of rotation of the crankshaft, in each case a rising or falling signal edge of the a signal (S1, S2) and the signal level of the other signal (S1, S2) is used and wherein from both electrical signals (S1, S2) a pulse length coded encoder signal (PL) is generated whose period is equal to those of the signals of the encoder ( 6 . 7 ) and whose pulse length codes the direction of rotation of the crankshaft, characterized in that a mean pulse length (PL_fil) is formed from the pulse length coded encoder signal (PL) and the pulse length of the encoder signal (PL) for determining the direction of rotation of the crankshaft with the average pulse length (PL_fil ) is compared. Method according to claim 1, characterized in that the mean pulse length (PL_fil) a mean over the time is. Method according to one of the preceding claims, characterized characterized in that the mean value of the pulse length (PL_fil) Threshold for the assignment of the pulse length of the pulse length coded Encoder signal (PL) to a direction of rotation. Method according to the preceding claim, characterized characterized in that the threshold value consists of a constant ratio (K) the pulse length is determined. Method according to the preceding claim, characterized characterized in that the threshold value according to S = (K + 1) / (2 * K) * PL_fil from the constant ratio (K) the pulse length is determined Method for operating an internal combustion engine with a sensor disk ( 1 ), which is coupled to a crankshaft of the internal combustion engine, wherein the encoder disc ( 1 ) a mark ( three ) by alternating arrangement of teeth ( 4 ) and tooth gaps ( 8th ), and wherein the encoder disc ( 1 ) a first donor ( 6 ) as well as a second donor ( 7 ), each of which can generate an electrical signal (S1, S2) 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 In addition, for determining the direction of rotation and increment of the angle of rotation of the crankshaft in each case a rising or falling signal edge of the one signal (S1, S2) and the signal level of the other signal (S1, S2) is used and wherein from two electrical signals (S1, S2) a pulse length coded encoder signal (PL) is generated whose period is equal to those of the signals of the encoder ( 6 . 7 ) and whose pulse length encodes the direction of rotation of the crankshaft, whereby a counter for the crankshaft angle is incremented or decremented, characterized in that the state of the counter is compared with the actual crankshaft angle when the zero mark on the sender wheel is reached. Internal combustion engine with a sensor disk ( 1 ), which is coupled to a crankshaft of the internal combustion engine, wherein the encoder disc ( 1 ) a mark ( three ) by alternating arrangement of teeth ( 4 ) and tooth gaps ( 8th ), and wherein the encoder disc ( 1 ) a first donor ( 6 ) as well as a second donor ( 7 ), each of which can generate an electrical signal (S1, S2) 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 In addition, for determining the direction of rotation and increment of the angle of rotation of the crankshaft, in each case an increasing or falling signal edge of one signal (s1, S2) and the signal level of the other signal (S1, S2) is used, and wherein from both electrical signals (S1, S2) a pulse length coded encoder signal (PL) is generated whose period is equal to those of the signals of the encoder ( 6 . 7 ) and whose pulse length codes the direction of rotation of the crankshaft, characterized in that a threshold value (S) is formed from the pulse-length-coded transmitter signal (PL) and the threshold value (S) and the unfiltered pulse-length-coded transmitter signal (PL) are applied to a comparator. Internal combustion engine according to the preceding claim, characterized in that the pulse length coded encoder signal (PL) for thresholding initially with a low pass filter (TP) Internal combustion engine according to the preceding claim, characterized in that the filtered signal PL_fil a amplifier supplied which forms a threshold S = (K + 1) / (2 * K) * PL_fil. control unit for one Internal combustion engine according to one of claims 7 to 9, which is a method according to one of the claims 1 to 6 can.