EP1815110B1 - Method for calibration of a positional sensor on a rotational actuator device for control of a gas exchange valve in an internal combustion engine - Google Patents

Abstract

A method for calibrating a distance sensor of a rotary actuator device for controlling a charge cycle valve of an internal combustion engine. The rotary actuator device includes a controllable electric motor having an actuator element for actuating the charge cycle valve, two energy storage means acting in opposite drive directions on the charge cycle valve, a control and regulating device which controls the electric motor with regard to its rotor angle according to a stored setpoint path and a distance sensor for detecting the rotor position. At least one state variable of the electric motor is measured, the at least one state variable being compared with a reference variable. If there is a deviation between the variables being compared, the stored setpoint path and/or the distance sensor signal detected is/are altered as a function of the state variable.

Description

The present invention relates to a method for calibrating a displacement sensor of a Drehaktuatorvorrichtung for controlling a gas exchange valve of an internal combustion engine according to the preamble of claim 1. In particular, the method finds application in Drehaktuatorvorrichtungen without mechanical stops.

In conventional internal combustion engines, the camshaft for controlling the gas exchange valves is mechanically driven by a timing chain or a timing belt from the crankshaft. To increase the engine performance and to reduce fuel consumption, it brings considerable advantages to individually control the valves of the individual cylinders. This is possible by a so-called fully variable (variable timing and variable valve lift), for example, a so-called electromagnetic valve train. In the case of a fully variable valve train, an "actuator unit" is assigned to each valve or "valve group" of a cylinder. Currently, different basic types of actuator units are being researched.
In a basic type (so-called stroke actuators), a valve or a valve group is associated with an opening and a closing magnet. By energizing the magnets, the valves can be moved axially, ie opened or closed.
The other basic type (so-called rotary actuator) is a control shaft provided with a cam, wherein the control shaft is pivotable by an electric motor back and forth.

To control a rotary actuator, most accurate sensor values are required which represent information about the instantaneous position of the rotary drive element and / or the element driving the drive element of the rotary actuator itself, e.g. The position of the rotor-driven actuator (e.g., camshaft) or the rotor position itself. In known rotary actuator devices, displacement sensors are each calibrated by the approach of mechanical stops that define the end positions of a control cam.

From the DE 101 40 461 A1 is a Drehaktuatorvorrichtung for stroke control of a gas exchange valve with such mechanical attacks known. The stroke control of the gas exchange valves takes place here via a map-controlled electric motor, on whose rotor a shaft is arranged with a rotatably connected control cam. During operation of the internal combustion engine pivots, or oscillates the rotor of the electric motor back and forth and the control cam presses via a pivot lever periodically the gas exchange valve in its open position. The gas exchange valve is closed by the spring force of a valve spring. So that the electric motor does not have to overcome the entire spring force of the valve spring when opening the gas exchange valve, an additional spring is attached to the shaft. The forces of valve spring and additional spring are such that during periodic operation of the rotary actuator device according to the position of the gas exchange valve, the kinetic energy is stored either in the valve spring (closing spring) or in the additional spring (opening spring). The device described proposes for the unique positioning of the control cam in its end positions, which is clearly positioned by means of a first and by means of a second rotation stop. A disadvantage of this arrangement, however, is that the calibration of displacement sensors for position determination by approaching mechanical stops does not have a satisfactory accuracy for all applications. Depending on the structure of the Drehaktuatorvörrichtung used, the mechanical tolerances of the system are so large that a required accuracy can not be achieved.

The object of the invention is to provide a method for measuring and calibrating a displacement sensor for a rotary actuator device, by means of which a more accurate positioning or position determination of the actuating element (and thus also of the gas exchange valve) is ensured. In particular, a method is to be specified, which ensures a measurement or calibration in both operating phases with low engine speed and operating phases with high engine speed in a reliable manner.

According to the invention the object is achieved by the entirety of the features of the independent claim. In this case, at least one state variable of the electric motor is determined and compared with a stored reference variable. In the case of a deviation between the determined state variable and the reference variable to be compared therewith above a predetermined value, the stored nominal path is controlled by means of which the electric motor or the rotor of the electric motor is controlled and / or the value detected by the displacement sensor as a function of the height the deviation of the state quantity from the reference value, changed.

The determination of the state variable is preferably carried out by measuring the corresponding value. Alternatively, however, the state variable can also be calculated on the basis of a stored model. Preferably, the state variable is the rotor angle, a time derivative of the rotor angle, and / or the motor current of the electric motor or one to the motor current proportional size (motor power, supply voltage of the electric motor) determined.

The change in the stored nominal trajectory and / or the detected travel sensor value preferably takes place by multiplying the stored desired trajectory values or travel sensor values by a correction factor and / or by adding a stored offset value. Correction factor and / or offset value are referred to below as the correction value. The correction value is determined as a function of the determined path deviation. The determination can be made by selecting from a stored stored table or by online calculation. At a high deviation (above a predetermined first deviation threshold), due to which the rotor threatens to fall, for example, in an unwanted intermediate position, a correspondingly high correction value is assigned, so that even in the same cycle or in the immediately subsequent cycle of the rotor this highly corrected values is regulated. A drop of the rotor in the described intermediate position is effectively prevented. In the case of a smaller path deviation, in the presence of which there is no risk of the rotor dropping off, the at least one monitored state value determined with each or every nth cycle can be averaged over a plurality of working cycles. An assignment or determination of a corresponding correction factor then takes place in particular on the basis of the averaged correction factor. As a working cycle in the context of the invention, in particular the opening or closing operation of a gas exchange valve or the immediately attributable thereto associated pivoting operation of the rotor of the electric motor is called. Also possible is a definition of the work cycle which includes closing and opening operation.

Since no gas counterpressures are to be taken into account during the closing process, the method according to the invention preferably takes place during the calibration of the displacement sensor during the closing process of the gas exchange valve assigned to the displacement sensor.

In particular, the method according to the invention comprises two different strategies for measuring or calibrating the rotary actuator. A first strategy is to detect smaller deviations of the rotor from the predetermined desired path by means of which it is controlled, averaging over a plurality of work cycles and depending on the averaged deviation to make a change in the desired path based on the rotor in the future and / or to change the path sensor signals in such a way that a correspondingly corrected path profile is adjusted in future due to the changed path sensor signals. This strategy extends over several working cycles (slow intervention). In contrast, the second strategy is to counteract larger deviations with a quick rule intervention. This is done by means of a corresponding change in the desired path and / or the Wegsensorsignale the control of the rotor already in the same or in the next cycle on the basis of the changed values of desired path and / or Wegsensorsignalen. However, the two strategies differ further in the measures to be taken, which will be discussed in the following description of the figures.

Figur 1:

die schematische Darstellung einer Drehaktuatorvorrichtung für den Antrieb eines Gaswechselventils einer nicht dargestellten Brennkraftmaschine,

Figur 2a-c:

veranschaulicht in drei unterschiedlichen Diagrammen die Zustandsgrößen Rotorwinkel, Rotorwinkelgeschwindigkeit und abgegebenes Drehmoment bzw. Stromaufnahme des Elektromotors, für den Fall, dass aufgrund eines Wegsensorfehlers kleineren Ausmaßes der Rotor sich über die Sollendposition hinaus bewegt,

Figur 3a-c:

veranschaulicht in drei unterschiedlichen Diagrammen die Zustandsgrößen Rotorwinkel, Rotorwinkelgeschwindigkeit und abgegebenes Drehmoment bzw. Stromaufnahme des Elektromotors, für den Fall, dass aufgrund eines Wegsensorfehlers kleineren Ausmaßes der Rotor nicht die Sollendposition erreicht,

Figur 4a-c:

die Zustandsgrößen gemäß Figur 2a-c für den Fall, dass aufgrund eines Wegsensorfehlers größeren Ausmaßes der Rotor sich über die Sollendposition hinaus bewegt,

Figur 5a-c:

die Zustandsgrößen gemäß Figur 3a-c für den Fall, dass aufgrund eines Wegsensorfehlers größeren Ausmaßes der Rotor nicht die Sollendposition erreicht, und

Figur 6:

zeigt den linearen Zusammenhang zwischen Wegsensor und Rotorwinkel im fehlerfreien und im fehlerbehafteten Fall.

In the following the invention will be explained in more detail with reference to figures. Show it:

FIG. 1:

the schematic representation of a Drehaktuatorvorrichtung for driving a gas exchange valve of an internal combustion engine, not shown,

Figure 2a-c:

FIG. 3 illustrates, in three different diagrams, the state variables rotor angle, rotor angular velocity and emitted torque or current consumption of the electric motor, in the event that the rotor moves beyond the setpoint end position due to a path error of smaller magnitude,

FIG. 3a-c:

FIG. 3 illustrates, in three different diagrams, the state variables rotor angle, rotor angular velocity and emitted torque or current consumption of the electric motor, in the event that the rotor does not reach the setpoint end position due to a path sensor error of lesser extent,

Figure 4a-c:

the state variables according to FIGS. 2a-c for the case in which the rotor moves beyond the setpoint end position due to a path sensor error of greater magnitude,

FIG. 5a-c:

the state variables according to FIG. 3 a - c in the event that the rotor does not reach the setpoint end position due to a path sensor error of greater magnitude, and

FIG. 6:

shows the linear relationship between displacement sensor and rotor angle in the faultless and faulty case.

Figure 1 shows the schematic representation of a rotary actuator for driving a gas exchange valve 2 of an internal combustion engine, not shown. The essential components of this device are, in particular designed as a servomotor electric motor 4 (drive means), one driven by this, preferably two cams 6a, 6b different hubs and rotationally fixed with the Rotor shaft connected camshaft 6 (actuator), one with the camshaft 6 on the one hand and with the gas exchange valve 2 on the other hand operatively connected rocker arm 8 (transmission element) for transmitting movement of the given by the cam 6a, 6b lifting height on the gas exchange valve 2 and a, the gas exchange valve 2 in Closing direction with a spring force acting on and designed as a closing spring first energy storage means 10 and, via the camshaft 6 and the drag lever 8, the gas exchange valve 2 with an opening force beaufschlagendes and designed as an opening spring second energy storage means 12. For the exact mode of action and mechanical design of the rotary actuator is on the DE 102 52 991 A1 referenced, which is included with respect content of the Drehaktuatoraufbaus in the disclosure of this application.

In order to ensure the lowest possible operation of the electric motor 4, which drives the existing gas exchange valve 2 via the camshaft 6, in addition to the optimal design of the counteracting springs (closing spring 10, opening spring 12) and the ideal positioning of rotation and articulation points in the Geometry of the device itself, the electric motor 4 via a control and regulating device 20 (hereinafter referred to as control device) according to a nominal path, which maps the ideal swing-out behavior of the spring-mass-spring system regulated. In particular, this control is done by controlling the rotor profile of the, at least one actuator 6, 6a, 6b driving electric motor 4. The ideal path of the rotor, which resonates as part of the vibration system is calculated analogously to the ideal waveform of the overall system and forms the desired path to Regulation of the electric motor 4. To monitor the actual position of the rotor, a non-illustrated displacement sensor is present, which transmits a sensor signal S to the control device 20 or another control device. The electric motor 4 is so by the Controlled control device 20 that the at least one gas exchange valve 2 from a first Ventilendlage E1, which corresponds for example to the closed valve position, in a second Ventilendlage E2, E2 ', for example, a partial (E2': partial stroke) or maximum open (E2: full stroke) Valve position corresponds, is transferred and vice versa. In the control of the electric motor 4, the rotor and thus the operatively connected to the rotor actuator 6, 6a, 6b controlled in position accordingly, so that the rotor or the actuator 6, 6a, 6b analogous to the closed position E1 of the gas exchange valve 2 a position in the range of travel of the cam base circle, eg in the directional range between R1 and R1 'occupy and analogous to the second end position E2, E2' a position in the direction of the cam 6a, 6b, eg in the path between R2 and R2 'occupy. The system is ideally designed so that the actuator 6, 6a, 6b in the exclusion (targeted disregard) of environmental influences (in particular friction and gas back pressure) the way between two end positions R1 - R2 (full stroke) or R1 '- R2' (partial stroke) without Infeed additional energy, ie without active drive by the drive device 4, travels and thus engages supportive only in the environmental conditions occurring in practice. The system is preferably designed such that it is in the maximum end positions R1, R2 of the rotor (vibration end positions at maximum vibration) each in a metastable torque neutral position in which the forces are in an equilibrium of forces and in which the rotor without applying a additional holding force is held.

In particular, in the first metastable and torque-neutral position R1 (shown in Figure 1) the gas exchange valve 2 is closed and thus the closing spring 10 while maintaining a residual preload maximum relaxed, while the opening spring 12 is biased to the maximum. The force of the prestressed opening spring 12 is via a stationary Supporting member 6c of the camshaft 6 transmitted to this and is directed in the position R1 exactly through the center of the camshaft 6 and thus virtually neutralized. The existing due to the residual bias force of the closing spring 10 is neutralized in the described position, as this is also directed via the cam followers 8 in the center of the camshaft 6.

In the second metastable and torque-neutral position R2, not shown, the gas exchange valve 2 would be opened with its maximum stroke according to the main cam 6b and the closing spring 10 arranged around the gas exchange valve 2 is biased to a maximum while the opening spring 12 would be maximally relaxed while maintaining a residual bias. The arrangement of the individual components is chosen such that again the force of the maximum prestressed spring means (now: closing spring 10) and the maximum relaxed spring means (now: opening spring 12) respectively directed through the center of the camshaft 6 and thus virtually neutralized in this position are.

A third, also not shown, stable and torque-neutral position R0 is present when the system assumes a so-called dropped state in which the camshaft 6 occupies a position between the two first metastable and torque-neutral positions R1, R2. From the fallen position, the system can be brought out again only by means of a high energy expenditure, in which, for example, by swinging or swinging the rotor, the camshaft 6 is again transferred to one of the first two metastable torque-neutral positions R1, R2 or the camshaft 6 at least up to a partial lift is swung, in which a regular operation of the rotary actuator device is possible again.

Analogous to the described three torque-neutral positions R0, R1, R2 for the operation of the device by means of the main cam 6b further positions (not shown) for a so-called minimum stroke operation upon actuation of the second cam 6a may be present. The same applies for these further torque-neutral positions as for the previously described torque-neutral positions R0, R1, R2.

In the case of the calculated ideal decay behavior, the rotor therefore oscillates from one end position E1, E1 'into the other end position E2, E2' solely on the basis of the energy stored in the energy storage means 10, 12 without the introduction of additional energy, for example by the electric motor 4.

In the event that the rotor in Teilhubbereich from a first end position R1 'to a corresponding second end position R2' oscillates (especially at high engine speeds), the ideal decay would thus be that of a perpetual motion (infinite constant vibration).

In the event that the rotor in Vollhubbereich from a first end position R1 to a corresponding second end position R2 oscillates (especially at idle or at low speeds of the internal combustion engine), he would be held in the end positions R1, R2 in a moment-neutral position and would have From this position, each time by introducing a pulse-like impulse energy (motor impulse) again caused to make the next oscillation in the other end position (therefore metastable torque-neutral position).

Due to the fact that the nominal paths for full stroke and partial stroke correspond to the decay behavior of the rotary actuator device without frictional losses and without gas counterpressures it is ensured that the Control device 20 controls the electric motor 4 exclusively to compensate for the ever-present in practice friction losses and the occurring gas back pressures. Since friction losses occur mainly at high rotor speeds, the electric motor 4 must deliver the highest power at high speeds. Since this coincides with the energy-optimal operating point of the electric motor 4, an energy-saving operation of the same can be ensured by the scheme based on idealized set paths of the actuator system to be operated.

In FIGS. 2 and 3, the state variables rotor angle, rotor angular velocity and output torque or current consumption of the electric motor are shown in three different diagrams ac in the case of smaller displacement sensor errors, while FIGS. 4 and 5 show the state variables for the sensor analogous to FIGS Case of larger sensor error show. In FIGS. 2-5, the setpoint values or the values to be expected on the basis of the setpoint path are in each case shown as uninterrupted lines and the actual values resulting from a deviation are shown as dashed lines.

FIGS. 2a-c describe the case in which the rotor of the electric motor 4 moves beyond the setpoint end position due to a faulty path sensor signal S (smaller extent error - within a predetermined first deviation range or below a first deviation threshold, respectively). The calibration of the displacement sensor takes place by evaluation of the state variables of the electric motor 4, preferably during the closing phase P _{closing of} a gas exchange valve 2. In this case, the specified by the desired path rotor target value in its end position by R2; R2 '(or the associated rotor angle RW (R2); RW (R2')) predetermined, the end position should be reached exactly at the boundary point between the opening phase P _opening and closing phase P _closing . Due to a present error-prone path sensor signal S, which upon reaching the desired rotor end position at R2; R2 '(target rotor end position) of the control device 20 suggests that the end position has not yet been reached, the expected maximum speed is exceeded at the time of rotation WP of the rotor movement (comparison of the actual path IB resulting from the control for the rotor angle profile with the predetermined desired path SB 2c) shows the rotor angle due to the (faulty) and already before the turning point WP in the time range B1 (Figure 2c) depending on the amount of deviation from at least one of the two state variables (rotor angular velocity, motor current consumption or For this purpose, the desired path to be corrected and / or the path sensor (value) to be corrected are subjected to a correction factor (multiplication) and / or an offset (addition) ,

Analogous to FIGS. 2a-c, the case is described in FIGS. 3a-c in that the rotor of the electric motor 4 does not reach the desired setpoint end position due to a faulty displacement sensor signal S (minor error - within a predetermined first deviation range). Due to a present faulty displacement sensor signal S, the control device 20 is suggested that already before reaching the desired rotor end position at R2; R2 '(target rotor end position) has already been reached (comparison of the actual control path IB due to the control for the rotor angle profile with the predetermined desired path SB on the basis of which the rotor angle was adjusted due to the (erroneous) displacement sensor signals). At the turning point WP of the rotor movement, the expected maximum speed is accordingly not reached (FIG. 3b), and an increased motor current consumption (or torque output) is already recorded before the point of turn WP (FIG. 3c). Depending on the amount of deviation from at least One of the two state variables (rotor angular velocity, motor current consumption or emitted electric motor torque) to the respective setpoint value of the state variable, a correction value for compensating the present error is also determined here. For this purpose, the setpoint path to be corrected and / or the path sensor (value) to be corrected are subjected to a correction factor (multiplication) and / or an offset (addition).
Accordingly, in the case of falling below the predetermined setpoint within the predetermined range, the change of the setpoint path SB and / or the Wegsensorsignals S made such that during a later cycle increased maximum stroke of the gas exchange valve 2 (compared to the maximum stroke reached in faulty Wegsensorsignalen according to actual IB), and in the event that the target value is exceeded, the change in the setpoint path SB and / or the path sensor signal S is made such that a reduced maximum lift of the gas exchange valve 2 is achieved during a later work cycle. This essentially results in a targeted displacement of the control technology defined end stops (and thus an adjustment of the maximum stroke) for the rotor of the electric motor.

In the case of a greater deviation (displacement sensor error of a greater extent-outside a predetermined second deviation range or exceeding a second deviation threshold), a rapid intervention immediately counteracts (FIG. 4a-c, FIG. 5a-c) by using a correction value associated with the present deviation (FIG. Correction factor and / or offset) as far as possible during the same or current work arcade, but at the latest in the next working cycle of the rotor this is controlled by means of a modified reference path SB or a modified path signal S of a newly calibrated displacement sensor. This is due to a deviation between the determined state variable and the reference size outside a predetermined Area a change in the desired trajectory SB and / or the displacement sensor signal S made such that the rotor is preferably still controlled in the same cycle on the basis of a modified desired trajectory and / or a modified Wegsensorsignals and in the following working cycle (without averages of the measured variables over several cycles) the maximum Hub is moved. In particular, in the case of falling below the setpoint outside the predetermined range, the change of the setpoint path SB and / or the Wegsensorsignals S made such that during the same cycle an early closing of the gas exchange valve 2 is achieved and in the following working cycle (without averaging the measured variables over several Working cycles), the maximum stroke is increased and so a later closing time is set again. In the event of exceeding the setpoint outside the predetermined range, the change of the setpoint path SB and / or the Wegsensorsignals S is such that during the same cycle a delayed closing operation of the gas exchange valve 2 is achieved and in the following working cycle (without averaging the measured variables over several Working cycles) the maximum stroke is reduced and a previous closing time is set again. As a result, there is essentially a rapid displacement of the closing control edge of the predetermined desired path SB.

FIG. 6 shows the linear relationship between the signal S of the displacement sensor (which depicts the position of the rotor) and the actually set rotor angle RW of the electric motor 4. In a faultless ideal case, for example, a characteristic according to K1 originating at zero point arises. If there is now an erroneous displacement sensor signal S, as a rule, a characteristic curve / straight line according to K2 or K3 is established, which is in each case rotated by one point on the error-free straight line. As already explained above, by computational correction, for example, by multiplication with a correction factor and addition of an offset (in general: Sensor_korrektur = Sensor_act × correction factor + offset) - each faulty characteristic again be converted into a fault-free characteristic. Based on the corrected characteristic curve, the displacement sensor can again supply error-free signals to the control device 20. As an alternative to the correction of the displacement sensor signals S, the setpoint path SB can also be adapted for the control of the rotor, or both correction options for parts can be carried out.

Claims (10)

1. A method for calibrating a positional sensor of a rotary actuator device for controlling a gas exchange valve of an internal combustion engine, wherein the rotary actuator device comprises:

   - a controllable electric motor (4) with an actuating element (6, 6a, 6b) for actuating the gas exchange valve (2),

   - two energy storage means (10, 12) acting in opposite drive directions on the gas exchange valve (2),

   - an open-loop and closed-loop control device (20), which controls the electric motor (4) with regard to its rotor angle according to a stored desired path (SB) in such a way that the rotor of the electric motor (4) is transferred from a first end position (R1; R1') into a second end position (R2; R2') and vice versa,

   - and a positional sensor for detecting the rotor position,

   characterised in that

   - at least one state variable of the electric motor (4) is determined,

   - the at least one state variable is compared with a reference variable, and

   - when there is a deviation between the variables to be compared, the stored desired path (SB) and/or the detected positional sensor signal (S) is changed as a function of the state variable.
2. A method according to claim 1, characterised in that the rotor angle (RW) or a time derivation of the rotor angle (RW) and/or the current consumption or the feed voltage of the electric motor (4) is determined as the state variable for the electric motor (4).
3. A method according to one or more of the preceding claims, characterised in that the adaptation of the desired path (SB) and/or the adaptation of the detected positional sensor signal (S) takes place by multiplication by a correction factor.
4. A method according to one or more of the preceding claims, characterised in that the adaptation of the desired path (SB) and/or the adaptation of the detected positional sensor signal (S) takes place by addition of an offset value.
5. A method according to one or more of the preceding claims, characterised in that the calibration of the positional sensor takes place during the closing process of the gas exchange valve (2) allocated to the positional sensor.
6. A method according to one or more of the preceding claims, characterised in that when there is a deviation between the determined state variable and the reference variable outside a predetermined range, a change in the desired path (SB) and/or the positional sensor signal (S) takes place in such a way that the rotor in the directly following working cycle is regulated with the aid of a changed desired path and/or a changed positional sensor signal.
7. A method according to claim 6, characterised in that if the desired value is fallen below outside the predetermined range, the change in the desired path (SB) and/or the positional sensor signal (S) takes place in such a way that during the same working cycle, a premature closing process of the gas exchange valve (2) is achieved, and in the case of an exceeding of the desired value outside the predetermined range, the change in the desired path (SB) and/or the positional sensor signal (S) takes place in such a way that, during the same working cycle, a delayed closing process of the gas exchange valve (2) is achieved.
8. A method according to one or more of the preceding claims, characterised in that in the event of a deviation between the determined state variable and the reference variable inside a predetermined range, a change in the desired path (SB) and/or the positional sensor value takes place in such a way that the rotor is regulated after a plurality of working cycles with the aid of a changed desired path and/or a changed positional sensor signal.
9. A method according to claim 8, characterised in that in the event of the desired value being fallen below inside the predetermined range, the change in the desired path (SB) and/or the positional sensor signal (S) takes place in such a way that during a later working cycle, an increased maximum lift of the gas exchange valve (2) is achieved and in that in the event of an exceeding of the desired value, the change in the desired path (SB) and/or the positional sensor signal (S) takes place in such a way that during a later working cycle, a reduced maximum lift of the gas exchange valve (2) is achieved.
10. A method according to claim 8 or 9, characterised in that the determined state variable is averaged over the plurality of working cycles and a change in the desired path (SB) and/or the positional sensor signal is made on the basis of the averaged state variable.

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