EP3081791A1 - Method for determining the shutoff position of a shaft of a combustion engine - Google Patents

Abstract

The invention relates to a method for determining the parking position of a shaft of an internal combustion engine, wherein the shaft comprises a transmitter wheel, which has a peripheral structure which triggers signals when moving past a sensor. According to the method, an electric machine is provided, in particular a starter generator, the rotor of which is rotationally fixedly connected to the shaft and which comprises a position detection device which is set up to detect an absolute rotor position within a pole pitch (R1). According to the method, a rotation reversal of the shaft is detected by means of the position detection device and detected rotational direction reversal detected absolute rotor position in the Abstellposition and within a pole pitch for correcting a determined by the encoder wheel stop position of the shaft (R2, G3).

Description

The invention relates to a method for determining the parking position of a shaft of an internal combustion engine, wherein the shaft comprises a transmitter wheel, which has a peripheral structure which triggers signals when moving past a sensor.

For internal combustion engines with a so-called stop-start function, an exact knowledge of the parking position of the internal combustion engine is necessary to shorten the start times. Already during the starting process, fuel injection can take place and this can be accelerated. Typically, an internal combustion engine has a Kurbelwellengeberrad, for example with 60-2 teeth, by means of which the position of the crankshaft can be determined to 3 ° accurate. Due to the temporal interpolation between two tooth flanks, the crankshaft angle can be resolved even finer with a rotating shaft. When the shaft is stationary, the angular position of the shaft can not be determined.

When stopping internal combustion engines, it may come to a reversal of the direction of rotation of the crankshaft due to restoring forces. If this direction of rotation reversal is not recognized, the parking position of the internal combustion engine is not determined correctly. Conventional methods using a sender wheel detect only the edge signal of a passing tooth of the sender wheel and are not designed to detect a reversal of direction.

From the EP 0 612 373 B1 However, a method for determining the parking position of a shaft of an internal combustion engine is known, which can detect a reversal of direction. By means of a cam and on a crankshaft mounted donor wheels and the respective sensors, a reversal of the direction of rotation of the engine is detected, so that in case of return oscillation of the internal combustion engine before standstill, the parking position can be corrected accordingly.

Furthermore, the describes DE 10 2009 000 082 A1 a method for detecting an engine stall during engine run-off having a crankshaft sensor wheel and a special crankshaft sensor capable of detecting the direction of rotation of the crankshaft. In each case, the last four registered pulse edges are stored and used to calculate the last three segment times. From these three calculated segment times becomes an upper limit for the time of occurrence of the next pulse edge estimated. If no further pulse edge occurs up to this estimated upper limit, it is concluded that the engine has come to a standstill.

Another generic method for determining the parking position of a shaft that can also determine a reversal of direction by means of a sensor wheel, is from the DE 10 2012 212 922 A1 known. It is proposed to calculate segment times from the time interval of the signals and to detect a direction of rotation reversal of the shaft as a function of the segment times.

A disadvantage of this known method for determining the parking position of a shaft is that a comparatively complex signal processing is required, which is associated with processing inaccuracies, so that the parking position can not be determined with sufficient accuracy.

It is thus an object of the invention to provide an improved method for determining the stop position of a shaft, with which disadvantages of conventional techniques can be avoided. The object of the invention is in particular to provide a method with which a reversal of the direction of rotation of the shaft can be reliably detected when stopping and the parking position can be precisely determined.

These objects are achieved by a method having the features of the main claim. Advantageous embodiments and applications of the invention are the subject matter of the dependent claims and are explained in more detail in the following description with partial reference to the figures.

The invention is based on the technical knowledge that increasingly internal combustion engines electric machines, especially starter generators, are installed, which are non-rotatably connected to a shaft, in particular the crankshaft, the internal combustion engine. Such known per se starter generators are usually provided between the engine and transmission in the form of a seated on the crankshaft electric machine with starter and generator function, which is commonly referred to as crankshaft starter generator (KSG), because of the direct connection of its rotor with the Crankshaft of the internal combustion engine. In conventional starter generators, an accurate pole position detection is necessary because the currents in the stator winding must be controlled synchronously or asynchronously with the current magnet position of the rotor. Known starter generators therefore have a position detection device for speed control of electrical machine, which is set up to determine an absolute rotor position within a pole pitch high-resolution. The position detection device can be designed as a resolver. But there are also known position detection devices that operate resolverlos (see. DE 10 2013 203 937 A1 ). Is installed on the internal combustion engine such a starter generator with a position detection device, this can be used according to the invention to reliably detect a reversal of rotation of the shaft when stopping and use a detected by the position detection Rotorendlage in the parking position for correcting the determined by means of the encoder wheel stop position of the internal combustion engine , Additional components for detecting the direction of rotation reversal and / or complex and error-prone evaluation methods, such as, for example, for determining the change in the segment times of the encoder wheel during leakage, can then be dispensed with.

According to general aspects of the invention, a method is thus provided for determining the parking position of a shaft of an internal combustion engine. The shaft is preferably a crankshaft of the internal combustion engine. The shaft comprises a sensor wheel in a manner known per se, which has a peripheral structure which triggers signals when moving past a sensor. According to the method, there is further provided an electric machine, in particular a starter generator, whose rotor is non-rotatably connected to the shaft and which comprises a position detection device which is set up to detect an absolute rotor position within a pole pitch. According to the method, a reversal of the direction of rotation of the shaft when the internal combustion engine is switched off is detected by means of the position detection device. If such reversal of direction of rotation is detected, a detected absolute rotor position in the parking position and within a pole pitch is used to correct a stop position of the shaft determined by means of the encoder wheel.

The absolute rotor position within a pole pitch indicates an absolute rotor position of the electric machine relative to the pole pitch and is thus dependent on the number of pole pairs of the electrical machine. Depending on the number of pole pairs a full revolution of the rotor is divided into individual segments (pole pitches). The rotor position detected by means of the position detection device thus unambiguously indicates the angular position within a pole pitch, but is ambiguous with respect to the angular position with respect to the full revolution or in which of the segments is measured. The position detection device thus generates within a pole pitch an absolute angle signal, on the course of which a direction of rotation reversal is directly readable. The position detection device can reverse the direction of rotation, for example, by means of a reciprocating movement or an increase and subsequent decrease in the detected absolute rotor position within a pole pitch at a coasting of the rotor, ie within a suitably predetermined time interval before the parking position, recognize. The detected absolute rotor position in the parking position and within a pole pitch thus indicates the end position of the rotor with the engine off, from which the Abstellposition the shaft is derivable, since the rotor is rotatably connected to the shaft.

According to a particularly preferred embodiment, the detected absolute rotor position in the parking position and within a pole pitch of an evaluation unit of a control device (control unit) for controlling the ignition and / or injection of the internal combustion engine is supplied. This offers the advantage that the evaluation unit or the control unit with this information can optionally correct the parking position determined by means of the encoder wheel, z. B. within a stop phase of a stop-start operation in order to determine the correct injection timing at the next start can. This embodiment is particularly advantageous in powertrain configurations in which separate control devices are provided for the control of the ignition and / or injection of the internal combustion engine and for the operation of the electric machine, which is usually required for the real-time capability of the control.

According to a preferred embodiment, the position detection device is a resolver of the electrical machine, in particular a Mehrpolpolpaarresolver. It has already been mentioned above that the position detection devices can also be a resolverless position detecting device.

A further possibility of the invention provides that in a detected reversal of rotation, the specific stop position of the shaft is determined by a value of the detected absolute rotor position in the Abstellposition and within a pole pitch, wherein the value is corrected by a predetermined phase offset between the encoder wheel and position detection device and a Unambiguity of this value is resolved with respect to the present pole pitches or with respect to the present pole position based on the detected by the sender wheel off position. According to this variant, it is thus proposed, in the case of a detected direction of rotation reversal, to determine the stop position of the shaft in the stop position on the basis of the determined angular position of the rotor, wherein the detected stop position of the encoder wheel is merely used to determine the current pole position or the current segment this is the specific angular position of the position detection device refers to calculate a unique angular position of the ambiguous signal of the position detection device.

The sender wheel may be a conventional sender wheel, in particular a 60-2 sender wheel.

According to a further aspect of the invention, a control device is proposed, which is designed to carry out a method as disclosed herein. The invention further relates to a motor vehicle, in particular a commercial vehicle, comprising such a control device.

Figur 1

ein schematisches Ablaufdiagramm gemäß einer Ausführungsform der Erfindung und

Figur 2

Diagramme, die den beispielhaften zeitlichen Verlauf des Resolversignals, des Geberradsignals und des korrespondierenden Wellendrehwinkels illustrieren.

The preferred embodiments and features of the invention described above can be combined with one another as desired. Further details and advantages of the invention will be described below with reference to the accompanying drawings. Show it:

FIG. 1

a schematic flow diagram according to an embodiment of the invention and

FIG. 2

Diagrams that illustrate the exemplary time profile of the resolver signal, the encoder wheel signal and the corresponding shaft rotation angle.

FIG. 1 shows a schematic flow diagram according to an embodiment of the invention. The flowchart schematically describes the determination of the stop position of a crankshaft of an internal combustion engine, hereinafter also referred to as an internal combustion engine, wherein the crankshaft comprises a transmitter wheel having a peripheral structure which (not shown) in passing on a sensor signals 5 triggers.

In the present case, the sender wheel is a 60-2 sender wheel, ie, the sender wheel has 60 similar angle marks, two of which are missing, which have been milled out, for example, in order to generate a reference signal for determining the position on the basis of the gap. The term circumferential structure of the encoder wheel is to be interpreted broadly and z. B. in the form of markings or a tooth structure. Typically, the peripheral structure is formed from ridge-shaped or tooth-shaped radial projections and grooves or tooth spaces lying therebetween. The encoder wheel is part of an arrangement for non-contact determination of the rotational speed of the shaft and further comprises a magnetically or optically operating sensor (speed sensor), which is arranged stationary to the encoder wheel, so that the peripheral structure is moved past the sensor device. If the sensor works magnetically, it is equipped with a magnetic field sensor (eg Hall sensor). This is from a Magnet in the field of Hall sensors generates a magnetic field, which changes when passing a tooth of the gear. The Hall sensor detects this once the so-called basic field of the magnet. To this field strength of the basic field, a field strength originating from the mass of the encoder wheel is added. If a tooth is then assigned to the sensor instead of a tooth gap, this leads to a repeated amplification of the magnetic field for the duration of the assignment of the tooth to the sensor. Thus, when the gear rotates, there is a fluctuation of the field strength in response to the passing of the teeth and tooth gaps on the sensor. The Hall sensor thus detects this change in the magnetic field and generates an electrical signal from which the speed or a setting angle of the gear can be determined. Each tooth thus gives a pulse, and by counting the pulses you can determine the speed. More specifically, the speed sensor does not recognize the tooth as such, but each transition from tooth to tooth gap or vice versa.

The time course 5 of such an electrical signal when switching off the internal combustion engine is exemplified in the middle diagram of FIG. 2 shown. The successive detection of two flanks corresponds to a rotation angle of 3 °.

In normal operation of the internal combustion engine, the Geberradsignal in a conventional manner for speed and position detection of the crankshaft. A control device for controlling the ignition and / or injection of the internal combustion engine controls based on the detected speed and / or position of the ignition and / or injection of the internal combustion engine.

After switching off the ignition, the rotational speed of the crankshaft slows down until it comes to a standstill in a parking position. In the middle diagram of the FIG. 2 this can be recognized by the increasing distance between the edges of the rectangular signal. At time T0-1, the speed sensor measures the penultimate edge 6 and at time T0 the last edge 7 of the encoder wheel before standstill.

A control device for controlling the ignition and / or injection of the internal combustion engine, to which the signal 5 is applied, first interprets the last edge at time T0 as the 66 ° edge and determines the stop position as the 66 ° position (step G2).

In the present example, however, there was a return oscillation of the internal combustion engine and thus a reversal of the direction of rotation when the crankshaft was coasting. In fact, the sensor has Thus, the 63 ° edge of the encoder wheel detected twice, once in the forward movement and then again in the return movement after the reversal of direction, which is not apparent from the edge signal 7.

On the crankshaft, a starter generator is further arranged, whose rotor is rotatably connected to the crankshaft of the internal combustion engine. In the present case, the starter generator is designed, for example, as an eight-pole synchronous machine, so that eight segments (poles), each covering 45 ° of the entire circumference of the machine, result for the synchronous machine.

The starter generator comprises, as a position detection device for speed control, a resolver which is set up to determine an absolute rotor position within a pole pitch in a high-resolution manner. Within each segment, the resolver outputs an output signal for the rotation angle of the rotor in the range of -180 ° to + 180 °, which corresponds to a total rotation angle of the crankshaft of 360 ° / 8 = 45 °. The phase offset between resolver and encoder wheel was assumed to be 0 °.

The corresponding time course 1 of the resolver signal during shutdown of the internal combustion engine is in the upper diagram of FIG. 2 shown. The corresponding time course 8 of the angle of rotation of the crankshaft during shutdown of the internal combustion engine is in the lower diagram of FIG. 2 shown.

It can be seen that a passage through an angle range from -180 ° to + 180 ° of the resolver (first segment in the upper diagram of FIG FIG. 2 ) corresponds to a rotation angle of 45 ° of the crankshaft.

During normal operation of the electric machine, the resolver continuously determines the rotor position for regulating the speed of the machine (step R1). The steps G1 and R1 are executed in parallel and independently of each other in normal operation.

Since the resolver indicates an absolute rotor position within a pole pitch, a reversal of the direction of rotation can be detected directly on the time profile. In the present case, the resolver detects in step R2 that at a rotor position 2 of -30 ° and at time T1, a reversal of direction has taken place, since the time course of the rotor position after T1 drops again to a value of the rotor end position 3 from -42 ° to time T2 on which the rotor and thus also the crankshaft came to a standstill.

The corresponding reversing position and parking position of the crankshaft are indicated in the lower diagram by the reference numerals 9 and 10.

The rotor stall of -42 ° determined in step R2 and the time T1 and optionally the time T2 are transmitted in step R3 via the CAN data bus of the vehicle to the control device for controlling the ignition and / or injection of the internal combustion engine. This gives the control device the information that it has come at -30 ° rotor position and at time T1 to a reversal of direction and that the rotor of the starter generator has come at an angular position of -42 ° at time T2 to the style.

With this information, the control device for controlling the ignition and / or injection of the internal combustion engine in step G3 perform a correction of the determined parking position.

The control device detects by adjusting the time T0 (time of the last edge measurement) with the times T1 and T2 that the last edge after the time T1 and thus after the reversal of direction was measured, so that the determined in step G2 parking position of 66 ° not it is correct, because instead of the 66 ° -flank the 63 ° -flank was measured twice.

The control device can then determine the actual parking position based on the value of -42 ° of the detected absolute rotor position in the parking position and within a pole pitch. From the last edge 7 of 66 ° determined by means of the sender wheel in step G2, the control device can determine that the value of -42 ° indicates the absolute rotor position in that segment which lies between 45 ° and 90 °. Since the phase offset between encoder wheel and resolver is 0 ° in the present case, the parking position of the crankshaft, d. H. the angular position of the crankshaft at which the internal combustion engine has come to a standstill as 62.2 ° according to the calculation rule (360 ° + (180 ° + α)) / n = 62.2 °, for α = -42 ° and n = 8 (Number of segments or pool pairs). The above calculation rule only applies to the segment lying between 45 ° and 90 °.

The value of 62.2 ° can thus be defined as a corrected parking position.

If, on the basis of the last flank 7 determined by means of the sender wheel in step G2, it is determined that the value 3 of the rotor end position lies in another segment, a calculation rule assigned to another segment must accordingly be used.

Although the invention has been described with reference to particular embodiments, it will be apparent to those skilled in the art that various changes may be made and equivalents may be substituted for without departing from the scope of the invention. In addition, many modifications can be made without leaving the associated area. Accordingly, the invention should not be limited to the disclosed embodiments, but should include all embodiments which fall within the scope of the appended claims. In particular, the invention also claims protection of the subject matter and the features of the subclaims independently of the claims referred to.

LIST OF REFERENCE NUMBERS

1

Time course of the resolver signal

2

Rotor position at the time of reversal

3

Rotor position in the parking position

5

Time course of the sensor wheel speed sensor

6

Penultimate flank

7

Last flank

8th

Time course of the rotational position of the crankshaft

9

Reversal of the crankshaft

10

Parking position of the crankshaft

Claims (8)

A method for determining the parking position of a shaft of an internal combustion engine, the shaft comprising a transmitter wheel having a peripheral structure that triggers signals (5) when moving past a sensor,
marked by an electric machine whose rotor is connected in a rotationally fixed manner to the shaft and which comprises a position detection device which is set up to detect an absolute rotor position (1) within a pole pitch (R1), wherein a direction of rotation reversal (9) of the shaft is detected by the position detection device and detected rotational direction reversal detected absolute rotor position (3) in the Abstellposition and within a pole pitch for correcting a determined by the encoder wheel stop position of the shaft is used (R2, G3). A method according to claim 1, characterized in that the detected absolute rotor position (3) in the parking position and within a pole pitch of an evaluation of a control device for controlling the ignition and / or injection of the internal combustion engine is supplied (R3). Method according to one of claims 1 or 2, characterized in that the position detection means detects the direction of rotation reversal based on a reciprocating motion of the detected absolute rotor position (1) within a pole pitch in a runout of the rotor. Method according to one of the preceding claims, characterized in that the position detection device is a resolver of the electric machine, in particular a Mehrfachpolpaar-resolver. Method according to one of the preceding claims, characterized in that at a detected direction of rotation reversal, the specific stop position of the shaft is determined by a value (3) of the detected absolute rotor position in the Abstellposition and within a pole pitch, the value by a predetermined phase offset between encoder wheel and Position detection device is corrected and an ambiguity of the value is resolved with respect to the present pole pitches based on the detected by the encoder wheel off position. Method according to one of the preceding claims, characterized (a) that the electric machine is a starter generator, in particular a crankshaft starter generator; and or (b) that the shaft is a crankshaft; and or (c) that the encoder wheel is a sensor wheel 60-2. Control device, which is designed for carrying out a method according to one of the preceding claims. Motor vehicle, in particular commercial vehicle, comprising a control device according to claim 7, which is designed for carrying out a method according to one of the preceding claims.

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