EP2150697B1 - Method for positioning a crankshaft of a turned-off internal combustion engine of a motor vehicle - Google Patents

Abstract

The invention relates to a method for positioning a crankshaft of a turned-off internal combustion engine of a motor vehicle, wherein the crankshaft is rotated into a desired target position for the subsequent start of the internal combustion engine by means of an electric starter motor having a free wheel. The invention provides that at least one characteristic curve and/or characteristic value of a correlation between a covered rotational distance of the crankshaft and a position of the angle of rotation is determined at a standardized pulsed current duration of the starter motor for a defined operating case, that the current position of the angle of rotation of the crankshaft is determined, and that at least one estimated pulsed current duration is applied to the electric starter motor as a function of the determined position of the angle of rotation of the crankshaft and the target position and the characteristic curve/characteristic values. The invention further relates to a device for carrying out the method according to one or more of the preceding claims, comprising at least one electric starter motor having a free wheel, and a controller actuating the starter motor, and a sensor for detecting the current position of the angle of rotation of a crankshaft of an internal combustion engine.

Description

The invention relates to a method for positioning a crankshaft of a disconnected internal combustion engine of a motor vehicle, wherein the crankshaft is rotated by means of a freewheel having, electric starter motor in a desired target position for the subsequent start of the internal combustion engine.

State of the art

For starting internal combustion engine starter motors are generally used, which engage a so-called starter pinion for engagement with a ring gear of the crankshaft and rotate the crankshaft on the thus created sprocket gear engagement with the engine stationary. Here, the crankshaft is set in a rotational movement before a first ignition takes place. After switching off the internal combustion engine, the crankshaft comes to a standstill in a stable angular position. However, this rotational position may be unfavorable for a subsequent start of the engine, for example, if none of the stored in the cylinders of the engine piston are in a favorable position for ignition.

From the DE 10 2005 004 326 A1 a method of the type mentioned is known in which the crankshaft is brought to a optimal for the start of the internal combustion engine target position at standstill of the internal combustion engine. For this purpose, the starter motor is operated until the crankshaft has reached the target position. Due to the freewheel of the starter motor, the rotational movement of the crankshaft can be influenced by the starter motor only in one direction of rotation. The starter motor can not slow down the rotation of the crankshaft. Depending on its rotational position, the crankshaft has a different rotational behavior with respect to its torque. Depending on Rotation angle position, the crankshaft can be acted upon by a positive or negative torque. The negative torque can result in the crankshaft overtaking the starter motor. This in turn can lead to the desired target position being crossed over.

DE 10 2005 027728 discloses how, directly after switching off, by means of the starter, the crankshaft is brought into a predetermined angular position in which the loose-release torque is relatively low.

Disclosure of the invention

The invention provides that at least one characteristic and / or characteristic values of a relationship between a traversed crankshaft rotational travel and a rotational angular position at a normalized pulse duration of the starter motor for a defined operating case is determined, that the current rotational angular position of the crankshaft is determined and that the electric starter motor Depending on the determined rotational angular position and the target position of the crankshaft and the characteristic / characteristic values is acted upon with at least one estimated pulse current duration. In the method according to the invention, therefore, at least one characteristic curve and / or characteristic values are first determined which determine the relationship between the traversed crankshaft rotational travel and a rotational angular position from which the rotational path of the crankshaft is traveled at a normalized pulse current duration applied to the starter motor , determined for a defined operating case. Expressed in even simpler terms, it is thus determined for a defined operating case how far the crankshaft moves or rotates from a specific rotational angle position in the case of a standardized pulse current duration. Advantageously, the relationships described are determined for a large number of rotational angle positions of the crankshaft, in particular rotational angle positions in the region of stable positions of the crankshaft being taken into account. The higher the number of angles of rotation considered, the more accurately the crankshaft can be positioned. The characteristic curve and / or the characteristic values are preferably determined once in advance, the characteristic curve and / or the characteristic values advantageously being stored in a non-volatile memory of a control device controlling the starter motor, so that they can be called up at any time. In order to rotate the crankshaft to the desired target position, the current rotational angular position of the crankshaft is first determined when the internal combustion engine is switched off or stationary. This can be done easily by means of a common sensor respectively. Of course, the signal of an existing, corresponding sensor of the internal combustion engine can be used. Depending on the rotational angle position of the crankshaft, the necessary turning path for reaching the target position, in particular the nearest target position, is determined. Finally, the electric starter motor is subjected to at least one estimated pulse current duration to reach the target position as a function of the determined values. The starter motor is therefore subjected to a pulse current duration, which is dependent on the determined current rotational position and the (nearest) target position and the "known", previously determined behavior (characteristic / characteristic values) of the crankshaft, in particular by means of the characteristic / characteristic values, the pulse current duration can be estimated. The estimation is advantageously carried out as a function of at least one further parameter. By the previously determined characteristic curve (and / or characteristic values), the torques of the crankshaft which are dependent on the rotational angle position are taken into account. As a result, the required pulse current duration for the starter motor can also be estimated in a simple manner, and the crankshaft can be moved to the desired target position. Conveniently, the desired target position is located in a stable region of the crankshaft.

According to a development of the invention, the pulse current duration is estimated such that the electric starter motor must be subjected to at least one further pulse current duration for reaching the target position. So that the desired target position is not run over, the pulse current duration is thus estimated "conservatively". This means that the pulse current duration is distributed according to the measure that the desired target position is usually reached only after a second current pulse. As a result, a quick setting of the desired target position is realized in a simple manner.

After applying the electric starter motor with the (first) pulse current duration, a further rotational angular position of the crankshaft, which has come to a standstill, is advantageously determined for this purpose. After the starter motor has thus been charged with the (first) pulse current duration, the Rotational position of the crankshaft, once it has come to a standstill in a stable position, determined again.

Furthermore, it is provided that the further (second) pulse current duration is estimated in dependence on the further determined rotational angular position of the crankshaft and the previously determined characteristic curve / characteristic values. In other words, in the event that the crankshaft is not yet in the target position after the first (first) estimated pulse current duration, the method described above is repeated, taking into account the new rotational angular position in the estimation of the further (second) pulse current duration becomes.

In an advantageous embodiment of the invention, the electric starter motor is subjected to a maximum of three current pulse durations or three current pulses for reaching the target position. The approach of the crankshaft to the target position is thus limited to a maximum of three steps, so that a rapid adjustment of the crankshaft. By taking account of current parameters when estimating the respective pulse current duration, however, the target position or the target region is usually already reached after the second pulse current. Advantageously, a tolerance range is defined around the target position in which the crankshaft can be located for an optimal quick start of the internal combustion engine. In other words, a target range is specified, in which the crankshaft is to be rotated for a subsequent start of the internal combustion engine.

Advantageously, the voltage of an energy storage device supplying the electric starter motor with electrical energy is taken into account for estimating the pulse current duration. In particular, the deviation of a maximum possible voltage from a normalized voltage level is taken into account so that the pulse current duration is estimated to be shorter or longer. In addition, by taking into account the operating state of the energy storage and a voltage drop in the electrical system of the motor vehicle is prevented.

According to a development of the invention, the current temperature of the internal combustion engine is taken into account for estimating the pulse current duration. The temperature of the internal combustion engine has particular effects on the friction values of the internal combustion engine. These in turn have a direct effect on the movement or the torque of the crankshaft. Especially at high temperatures, when the internal combustion engine has warmed up, the torque of the crankshaft is lower than at low temperatures. Additionally or alternatively, the operating time of the internal combustion engine can also be taken into account, which, for example, affects the viscosity of a lubricant and the temperature of the internal combustion engine.

Furthermore, an estimation factor which is determined as a function of the difference / deviation of the current rotational angular position of the crankshaft relative to the target position is advantageously taken into account for estimating the pulse current duration. In the case of a large deviation of the current rotational angular position of the crankshaft from the target position, a larger estimation factor is expediently provided, that is to say one which extends or corrects the pulse current duration upwards than at a small distance. As a result, the closer the crankshaft is to the target position, the smaller the movement or rotation of the crankshaft. As a result, the crankshaft is advantageously brought to the target position.

Furthermore, it is provided that the characteristic curve / characteristic values for a start-stop operation are determined as the operating case of the internal combustion engine. In order to reduce the fuel consumption of motor vehicles, in particular a shutdown of the internal combustion engine at longer stop times, such as traffic lights has proven. This shutdown can be implemented both manually by the driver and mechanically and electronically by the so-called start-stop operation. In this way, however, the starter motor is heavily loaded, moreover, the start time varies in the subsequent starting of the internal combustion engine in dependence on the rotational angular position in which the crankshaft comes to a stop after switching off the internal combustion engine. The fact that the characteristic curve / characteristic values are determined for a start-stop operation essentially means that the characteristic curve / characteristic values in the case of warmed up Internal combustion engine can be determined. The characteristic curve / characteristic values are preferably determined experimentally in advance and stored.

Advantageously, the starter motor is pre-loaded. This means that the drive pinion of the starter motor is already in engagement with a ring gear of the crankshaft when the crankshaft comes to a standstill, so that the energy supplied to the starter motor can be converted directly into a rotational movement. Alternatively, it is of course also conceivable that the drive pinion is meshed only after standstill of the crankshaft.

Furthermore, the invention relates to an apparatus for carrying out the above method with at least one freewheel having electric starter motor and a starter motor driving the control unit, and a sensor for detecting the current rotational angular position of a crankshaft of an internal combustion engine. According to the invention, the control device has a bypass circuit with current limiting, which is connected in parallel to a main circuit. This can be applied to the starter motor with current pulses to move the crankshaft to the desired target position / rotate without the main circuit is switched on. This makes it possible to separate from the positioning of the crankshaft from the actual starting or starting operation.

Brief description of the drawings

Figur 1

einen Startermotor einer Brennkraftmaschine in einer vereinfachten perspektivischen Darstellung,

Figur 2

ein Funktionsblockdiagramm eines Steuergeräts für den Startermotor,

Figur 3

ein Diagramm mit stabilen Drehwinkelbereichen einer Kurbelwelle der Brennkraftmaschine,

Figur 4

ein Flussdiagramm eines Ausführungsbeispiels des erfindungsgemäßen Verfahrens,

Figur 5

ein erstes Beispiel für die Anwendung des Verfahrens,

Figur 6

ein zweites Beispiel für die Anwendung des Verfahrens und

Figur 7

ein drittes Beispiel für die Anwendung des Verfahrens.

In the following, the invention will be explained in more detail with reference to some figures. Show this

FIG. 1

a starter motor of an internal combustion engine in a simplified perspective view,

FIG. 2

a functional block diagram of a controller for the starter motor,

FIG. 3

a diagram with stable rotation angle ranges of a crankshaft of the internal combustion engine,

FIG. 4

a flow chart of an embodiment of the method according to the invention,

FIG. 5

a first example of the application of the method,

FIG. 6

a second example of the application of the method and

FIG. 7

a third example of the application of the method.

Embodiment (s) of the invention

The FIG. 1 shows by way of example in a perspective view of a starter motor 1 of an internal combustion engine of a drive device of a motor vehicle, which has a einspurbares and / or voreinspurbares drive pinion 2. At the starter motor 1, a control unit 3 is arranged, which drives the starter motor 1. The control unit 3 has a connection device 4, to which a control device, not shown here, of the drive device can be connected. Furthermore, the control unit 3 has a connection device 5, to which a sensor for detecting the rotational angular position of a drivable by the starter motor 1 crankshaft 6 of the internal combustion engine can be connected. Im in FIG. 1 shown, einpurten state of the drive pinion 2 acts this with a rotatably connected to the crankshaft 6 ring gear 7 together, so that a rotational movement of the drive pinion 2 can be transmitted to the crankshaft 6. The starter motor 1 and the drive pinion 2 have a freewheel, so that the drive pinion 2 can only transmit a force in one direction of rotation.

The FIG. 2 shows a functional block diagram of the controller 3 of the starter motor 1 for a start-stop operation of the internal combustion engine. In start-stop operation, the internal combustion engine is temporarily switched off or switched off in phases in which it has no power to bring, such as when the motor vehicle is in front of a red light.
A control unit 8 of the drive device gives the control unit 3 of the control unit the start-stop operation. From the control unit 3 of Starter motor 1 is also driven a Einspurvorrichtung 9, which moves the drive pinion 2 axially to make it out of the in the FIG. 2 illustrated, nichteingespurten state in the in the FIG. 1 shown brought in-hook state. The control unit 3 furthermore has a bypass circuit connected in parallel to a main circuit with a current limitation realized by a series resistor R _V. This makes it possible to turn on the normally-trained starter motor 1 even in the engaged state, without the main circuit is closed.

The starter motor 1 can drive the crankshaft 6 of the internal combustion engine in only one direction in the engaged state. Depending on the angular position of the crankshaft thereby acts a load on the starter motor 1. The FIG. 3 shows in a diagram the behavior of the crankshaft in different rotational angle positions. The diagram shows the curve 10 of a crankshaft torque M over the rotational angle position α of the crankshaft. The course 10 has a substantially sinusoidal or cosinusoidal course over the rotational angle position α. In this case, the crankshaft per revolution passes through a plurality of pressing zones 11, 12, in which the torque is greater than zero, and a plurality of pulling zones 13, 14, in which the torque is less than zero. In the diagram, two lines 15 and 16 are further drawn, which define a region 17, which represents the friction torque of the internal combustion engine / represents. Above the line 15, a further region 18 is shown, which defines the inhibition torque of the starter motor 1. The inhibition torque of the starter motor 1 counteracts a back swinging of the crankshaft to a certain extent (about 10 Nm). Since the starter motor 1 can not decelerate the crankshaft 6 due to the freewheel, the restraining torque acts only on one side, with torques greater than zero. The curve 10 of the torque of the crankshaft has its maximum positive and negative values outside the regions 17 and 18.

In the sections of the course 10, which lie within the areas 17 and / or 18, there are so-called stable areas 19, 20, 21, 22, 23, in which the crankshaft 6 comes to a standstill after a shutdown of the internal combustion engine, since these areas, the friction torque of the internal combustion engine and / or the restraining torque of the starter motor 1 is greater than that Torque of the crankshaft 6 are. To ensure a quick start of the engine in start-stop operation, the crankshaft 6 by means of in the FIG. 4 twisted method shown in a desired target position, which is conveniently located in one of the stable regions 19 to 23.

The FIG. 4 shows in a flowchart an embodiment of an advantageous method for positioning the crankshaft 6 when the engine is switched off in the start-stop mode. In a first step 24, the method is started. In a subsequent query 25 is checked whether a start-stop operation of the drive device or the internal combustion engine is present. If this is not the case, for example, if the internal combustion engine is switched off by turning the ignition key, the method is ended in a subsequent step 26. If, on the other hand, a start-stop operation is present, then another inquiry 27 follows, in which it is checked whether the drive pinion 2 of the starter motor 1 has been meshed. As soon as this - the Einspuren - is done, followed by another query 28, in which the operating condition of the internal combustion engine is determined. Only when the internal combustion engine is at rest is another query 29. Here, the rotational angular position of the crankshaft 6 of the internal combustion engine is checked and compared with a target position or a target area. If the crankshaft 6 is in a rotational angle position which lies within a target range or corresponds to a target position, this leads to the abort of the method in step 26.

However, if it is determined by means of the above-mentioned sensor for detecting the rotational angular position of the crankshaft 6, that the crankshaft is in a rotational angular position outside the target area or a target position, another query 30, in which the quantity of deviation of the rotational angular position to the target position or to Target area is determined. If the deviation is only slight, then in a further step 31, a calculation of the distance of the angular position of the crankshaft 6 to the next / closest target position or to the next / next target range is carried out. In this case, an estimation factor is considered, which is determined as a function of the distance of the current rotational angular position of the crankshaft 6 to the target position / to the target area. If determined in the query 30, that the deviation from the target position is large, the estimation factor is corrected upward in a step 32 following the query 30.

The step 31 is followed in a step 33 by the determination of a pulse current duration which is applied to the starter motor 1 in the subsequent step 34 in order to move the crankshaft 6 into its target position or its target range. The upward corrected estimation factor causes a comparatively longer pulse duration. As soon as the crankshaft 6 of the internal combustion engine comes to a standstill again, which is determined by the query 28, it is checked again whether the current rotational angular position corresponds to the desired target position / target range (query 29). If this is the case, the method is ended in step 27.

However, if the crankshaft is still not in the target area or in its desired target position, the deviation from the target position in the query 30 is again determined, a corresponding estimation factor is specified and the starter motor 1 is charged with a specific pulse current duration. In the calculation of the pulse current duration in step 33, at least one predetermined characteristic and / or characteristic which includes a relationship between a traveled rotational travel of the crankshaft 6 and a rotational angular position at a normalized pulse current duration of the starter motor 1 for a start-stop operation. The characteristic curve or the characteristic values thus again indicate how far the crankshaft 6 moves out of a specific rotational angle position by acting on the starter motor 1 with a standardized pulse current duration. By means of these values, as described above, a necessary pulse current duration for reaching the target position can be estimated. In order to move the crankshaft 6 to its target position in as few steps as possible (maximum three), the estimated factor is predefined as a function of the abovementioned parameters, such as, for example, the rotational position of the crankshaft, the operating temperature of the internal combustion engine and / or the number of pulse streams. Advantageously, the estimation factor is predetermined in such a way that, in the case of a plurality of pulse currents, or in the case of several actuating movements of the starter motor 1 to achieve a target position, the pulse current duration is shortened from time to time.

In one in the FIG. 4 not shown method step, the method can be extended by the additional parameters in the determination of the pulse current duration in step 33, such as the operating temperature and / or operating time of the internal combustion engine and the current voltage level of the starter motor 1 supplying energy storage energy are considered.

In the following Figures 5 . 6 and 7 the advantageous method will be explained in more detail with reference to some practical examples. Where the Figures 5 . 6 and 7 among other things from the FIG. 3 well-known diagram, so on this the description of the FIG. 3 is referenced.

In the first in the FIG. 5 Example shown in step 29 of the method of FIG. 4 determines that the crankshaft 6 is in a rotational position 34 (indicated by arrow 34). Logically, the rotational angle position 34 is in a stable region 20. A nearest or target position 35 is in the same stable region 20. As a result, it is determined in the request 30 that the deviation to the target position 35 is low and the normally small predetermined estimation factor does not need to be corrected.

At the bottom of the FIG. 5 a second integrated diagram is shown, which represents the applied to the starter motor 1 voltage U over a time t. Due to the determined in step 30 small deviation from the target position 35 a small pulse current duration .DELTA.t ₁ is "known" as a function of the behavior of the crankshaft or of the characteristic curve / characteristic values are determined / calculated in the starter motor 1 is supplied with the voltage U. Since the crankshaft is in the stable region 20 6 decreases its rotational speed n, after the actuation of the starter motor 1 via the time .DELTA.t _1, due to the friction forces of the internal combustion engine rapidly until the crankshaft comes to a standstill at the target position. In the present case, therefore, a single application of the starter motor 1 with the pulse current width Δt _{1 is} sufficient to move the crankshaft to its target position 35.

The FIG. 6 shows a second example, which differs from the previous example in that the target position 35 is behind a pulling zone 13. The determined current angular position of the crankshaft 6 corresponds to the determined rotational angle position 34 from the FIG. 5 , It is thus in the stable region 20. However, the closest target position 35 is located in the stable region 21, which follows the pulling zone 13. In contrast to the previous example, in the method according to the FIG. 4 the estimation factor is corrected upward in step 32, since the deviation of the determined rotational angle position 34 from the target position 35 is large. With the aid of the determined characteristic curve / characteristic values, a first pulse current duration Δt ₂ is initially given "conservatively", with which the starter motor 1 is charged. As a result, the crankshaft 6 is moved out of the stable region 20 / rotated. The pulse current duration Δt ₂ is selected / estimated such that the starter motor 1 is switched off only after it has left the stable region 20. Due to the freewheel, the crankshaft 6 in the pulling zone 13 can continue to rotate until it comes to a standstill in the following stable region 21. This is exemplified by means of the speed n in the integrated diagram at the bottom of the FIG. 6 shown. Once the crankshaft is at a standstill, which is checked by the query 28, their current rotational position 36 is determined and compared with the target position 35 as described above. Since now the deviation from the target position 35 is low, a small pulse width Δt _{3 is} calculated with the aid of the previously determined characteristic curve / characteristics and the correspondingly chosen / determined estimation factor. The over the estimated pulse duration .DELTA.t ₃ acted upon starter motor 1 is accelerated such that the speed n of the crankshaft 6 then slowed down rapidly due to the friction forces of the engine until the crankshaft 6 comes to a standstill in the target position 35. As an alternative to a defined target position (35), of course, a target range can also be specified, in which the crankshaft 6 should be located.

The FIG. 7 shows an example of the case where the target position 35 is behind a pressing zone 14. In the example of FIG. 7 is in start-stop operation by means of the method of the FIG. 4 determines that the current rotational position 34 of the crankshaft 6 is in the stable region 21. This is the starter motor 1 due to the advantageous method with a pulse current duration .DELTA.t ₄ applied such that the crankshaft 6 is driven until it reaches the following stable area 22. This is necessary because the pressing zone 12 has to be bridged. Otherwise it could happen that the crankshaft 6 returns to the stable area 21 again. The pulse current duration is estimated in particular according to the known / determined torque behavior. As soon as the crankshaft 6 has come to a standstill in the stable region 22, as described above, a current rotational angle position 37 is detected again and compared with the target position 35. In the present example, the starter motor 1 is acted upon by the advantageous method with a pulse current duration .DELTA.t ₅ , whereby the crankshaft 6 is first accelerated. According to the advantageous method, the pulse current duration Δt ₅ is estimated in such a way that the rotational speed subsequently decreases in such a way that the crankshaft 6 comes to a standstill in the target position 35.

By the predicative method described above, in which the previously determined characteristics / characteristic curve (s) are used to determine a respective pulse current duration as a function of the current rotational angular position of the crankshaft 6, it is possible in a simple manner, the crankshaft 6 in a for to move the start of the engine advantageous position. The advantageous method offers the possibility to position the crankshaft 6 by means of a conventional starter motor 1. The method can be integrated in a simple and cost-effective manner in the control unit 3 of the starter motor 1 or alternatively, not shown here, in the control unit 8 of the drive device.

Claims (11)

1. Method for positioning a crank shaft of a turned-off internal combustion engine of a motor vehicle, wherein the crank shaft is turned, by means of an electric starter motor having a freewheel, into a desired target position for the subsequent starting of the internal combustion engine, characterized in that at least one characteristic curve and/or characteristic values of a relationship between rotational travel executed by the crank shaft and a rotational angle position given a standardized pulsed current period of the starter motor are determined for a specific operating case, in that the current rotational angle position of the crank shaft is determined, and in that at least one estimated pulsed current period is applied to the electric starter motor as a function of the determined rotational angle position of the crank shaft, the target position and the characteristic curve/characteristic values.
2. Method according to Claim 2, characterized in that a first pulsed current period is estimated in such a way that a further pulsed current period for reaching the target position has to be applied to the electric starter motor.
3. Method according to one of the preceding claims, characterized in that after a pulsed current period has been applied to the electric starter motor, a further rotational angle position of the crank shaft which has come to a standstill is determined.
4. Method according to one of preceding claims, characterized in that the further pulsed current period is estimated as a function of the further rotational angle position and the characteristic curve/characteristic values.
5. Method according to one of the preceding claims, characterized in that a maximum of three current pulse periods for reaching the target position are applied to the electric starter motor.
6. Method according to one of the preceding claims, characterized in that the voltage of an energy store which supplies the electric starter motor with electrical energy is taken into account in the estimation of the pulsed current period.
7. Method according to one of the preceding claims, characterized in that the current temperature of the internal combustion engine is taken into account in the estimation of the pulsed current period.
8. Method according to one of preceding claims, characterized in that an estimation factor, which is determined as a function of the distance between the present rotational angle position of the crank shaft and the target position is taken into account in the estimation of the pulsed current period.
9. Method according to one of the preceding claims, characterized in that the characteristic curve/characteristic values are determined for a start/stop operating mode as an operating case of the internal combustion engine.
10. Method according to one of the preceding claims, characterized in that the starter motor, in particular a drive pinion of the starter motor, is pre-meshed.
11. Device for carrying out the method according to one or more of the preceding claims, having at least one electric starter motor, which has a freewheel, and a control unit, which controls the starter motor, as well as a sensor for sensing the current rotational angle position of a crank shaft of an internal combustion engine, characterized in that the control unit has a bypass circuit with a current-limiting means connected parallel to a main circuit.

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