EP1812690A1

EP1812690A1 - Method for calibration of a positional sensor on a rotational actuator device for control of a gas exchange valve in an internal combustion engine

Info

Publication number: EP1812690A1
Application number: EP05857847A
Authority: EP
Inventors: Rudolf Dr. SEETHALER; Martin Lamprecht
Original assignee: Bayerische Motoren Werke AG
Current assignee: Bayerische Motoren Werke AG
Priority date: 2004-11-12
Filing date: 2005-10-19
Publication date: 2007-08-01
Also published as: US7516642B2; WO2006050796A1; DE102004054776B3; US20070208488A1

Abstract

The invention relates to a method for calibration of a positional sensor on a rotational actuator device for control of a gas exchange valve in an internal combustion engine. The rotational actuator device thus comprises a controlled electric motor, with an operating element for operating the gas exchange valve, two energy storage means, acting in opposing drive directions on the gas exchange valve and a controller, for controlling the electric motor. The controller controls the electric motor such that the gas exchange valve may be displaced from a first end position, in which the operating element driven by the electric motor by means of the rotor and hence the rotor, is in a metastable instantaneously-neutral position, corresponding to the first end position, into a second end position in which the operating element (6, 6a, 6b) and the rotor are in a metastable instantaneously-neutral position, corresponding to the second end position and vice versa. According to the invention, the electric motor is controlled from an instantaneously-neutral position, such that the rotor is displaced in at least one direction about a path run from the instantaneously-neutral position, the current draw for the electric motor arising therefrom is recorded and, depending on the obtained current values for the current draw of the electric motor, a new rotor position for calibration of the positional sensor is determined.

Description

Method for calibrating a displacement sensor of a rotary actuator device for controlling a gas exchange valve of an internal combustion engine

The present invention relates to a method for calibrating a displacement sensor of a rotary actuator device for controlling a gas exchange valve of an internal combustion engine according to the preamble of the independent claims.

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.

In the other basic type (so-called rotary actuator), a control shaft is 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 or the rotor position itself. In known rotary actuator devices, displacement sensors are each calibrated by starting mechanical stops that define the end positions of a control cam.

From DE 101 40 461 A1 a Drehaktuatorvorrichtung for stroke control of a gas exchange valve with such mechanical attacks is 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, the motor oscillates or reciprocates and the control cam periodically presses the gas exchange valve into its open position via a pivoting lever. 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 either in the valve spring (closing spring) or in the additional spring (opening spring) is stored. 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 position sensors for position determination by starting mechanical attacks not for all applications has a satisfactory accuracy. Depending on the structure of the Drehaktuatorvorrichtung 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 calibrating a displacement sensor for a Drehaktuatorvorrichtung, 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.

According to the invention, the object is achieved in each case by the entirety of the features of the independent claims.

In a first particularly preferred embodiment of the invention, in a rotary actuator according to the preamble of claim 1 starting from a metastable end position of the actuating element (here: camshaft) or starting from a metastable end position of the rotor of the electric motor of the electric motor driven such that the rotor to moves a distance in at least one direction out of its moment-neutral position and the resulting current consumption is detected. Subsequently, as a function of the detected current consumption, the displacement sensor for determining the rotor position or the position of the actuating element is neutral to a new, possibly corrected, torque Position (which ideally can be the same as the old position, or only slightly deviates from it) (calibrated).

In a preferred development of the invention, the rotor is deflected on both sides on the basis of a metastable torque-neutral position, the current consumption of the electric motor is observed, and the displacement sensor is adjusted to a corrected position, in particular to an adjusted metastable torque-neutral position. By slow movement (movement) of the rotor near the metastable torque-neutral end positions of the full stroke, the actual moment zero point can be determined at the self-adjusting current values (proportional to the restoring moment of the restoring torque acting on the rotor due to the respective tensioned opening or closing spring).

According to a second embodiment of the invention, in a rotary actuator according to the preamble of the second independent claim, the gas exchange valve is deliberately transferred to a torque-neutral center position, which in turn forms a unique reference point for the adjustment of the displacement sensor. This torque-neutral central position is in contrast to the above-described metastable end positions at full lift a stable position (so-called tapered or fallen position of the rotor) from the rotor can not be led out by a minimum impulse-like abutting energy. From this stable position, the rotor can be converted by a targeted arrival or swinging again in a Teil¬ or Vollhubbetrieb. This position corresponds to the position when the rotor uncontrollably slides off a metastable end position in full stroke and is therefore not desirable in normal operation. However, especially when starting a motor vehicle, there is sufficient time to carry out a calibration based on this procedure and then to swing the rotor back into a normal operating position. Further advantageous features of the invention are described in the dependent claims.

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

Figure 1: the schematic representation of a Drehaktuatorvorrichtung for driving a gas exchange valve of an internal combustion engine, not shown, and

Figure 2: the torque curve of opening and closing spring of a rotary actuator, which acts on the inlet side on a gas exchange valve and the adjusting stroke profile of the actuated gas exchange valve - shown schematically in a diagram.

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 an especially designed as a servomotor electric motor 4 (drive means), a driven by this, preferably two cams 6a, 6b different strokes and rotatably connected to the rotor shaft camshaft 6 (actuator), one with the camshaft 6 on the one hand and with the gas exchange valve 2 on the other hand in operative connection drag lever 8 (transmission element) for transmitting the movement of the given by the cam 6a, 6b lifting height to the gas exchange valve 2 and one, the gas exchange valve 2 in the closing direction with a spring force acting and designed as a closing spring first energy storage means 10 and a , via the camshaft 6 and the drag lever 8, the gas exchange valve 2 with an opening force acting on and designed as an opening spring second Energy storage means 12. Reference is made to DE 102 52 991 A1 for the exact mode of action and mechanical design of the rotary actuator device, which content is included in the disclosure content of this application with regard to the content of the rotary actuator structure.

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 controlled by the control device 20 such that the at least one gas exchange valve 2 from a first valve end position E1, which corresponds for example to the closed valve position, in a second valve end position E2, E2 \ for example, a partial (E2 ¹ : 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 transmitted to the camshaft 6 via a stationary support element 6c 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 moment-neutral position R2, which is not shown, the gas exchange valve 2 would be in accordance with its maximum stroke opened to the main cam 6b and the maximum arranged around the gas exchange valve 2 around closing spring 10, 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 RO is present when the system assumes a so-called dropped state in which the camshaft 6 assumes a position between the two first 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 RO, R1, R2 for the operation of the device by means of the main cam 6b further positions (not shown) for a so-called minimum lifting operation upon actuation of the second cam 6a may be present. The same applies for these further three torque-neutral positions as for the previously described torque-neutral positions RO, R1, R2.

In the case of the calculated ideal decay behavior, the rotor thus oscillates from one end position E1, E1 'to the other end position E2, E2' alone due to the stored energy in the means 10, 12 forces without feeding an additional energy, such as by the electric motor. 4

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

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

Due to the fact that the setpoint paths for full stroke and partial stroke correspond to the decay behavior of the rotary actuator device without frictional losses and without gas counterpressures, the control device 20 activates the electric motor 4 exclusively to compensate for the frictional losses and the occurring gas counterpressures which are always present in practice. 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 Figure 2, the torque curve of the two energy storage means 10, 12 (opening and closing spring) of the Drehaktuatorvorrichtung acting on a gas exchange valve and the adjusting stroke course of the actuated gas exchange valve 2 is shown schematically in a diagram. The curve K _M _s _c hiie _ßfede r the torque curve of the closing spring 10 and the curve K _M _öffnungsfeder the torque curve of the opening spring 12 during the opening operation of a gas exchange valve 2. To illustrate the opening process is analogous in the curve KHubveri _a uf the stroke of the driven Gas exchange valve 2 shown. In addition, the self-adjusting torque-neutral positions RO, R1, R2 are illustrated in the points PO, P1, P2. The first metastable and torque-neutral position R1 of the rotor or of the actuating element 6, 6a, 6b, during the closed state of the gas exchange valve 2 at full stroke, is located in the point P1 to the point in time when the opening spring curve K _M _ö _ff-voltage _fede r and When the curve of the opening spring curve K _M _opening spring intersects, the closing spring curve KM SchHeßfed _e r cuts positively. The second metastable and torque-neutral position R2 of the rotor or of the actuating element 6, 6a, 6b during the opening process of the gas exchange valve 2 at full stroke adjusts itself at the point P2 at the time when the Öffnungsfederkurve KM_öffnungsfeder and the Schließfederkurve KM_schiießfeder with decreasing curve of the opening spring curve KM_öffnungsfeder and also sloping curve of the closing spring curve KM_schiießfeder cut. The stable intermediate position RO described above (also called fallen or abgeschwungene position) is then present when opening spring curve K _M ö _ff voltage _sfede r and closing spring curve KM_schiie _ß spring then cut it when the opening spring curve K _M _öffnungsfeder during their falling waveform, the rising closing spring curve KM_schiie _ßf eder cuts. The torque curves shown are proportional to the respective resulting restoring moment of the spring forces and thus proportional to the current consumption of the electric motor 4. Starting from a metastable End position R1 or R2 into which the rotor or the rotationally fixedly connected actuating element 6, 6a, 6b is transferred on the basis of a predetermined control time using the measuring signal of the displacement sensor is checked at certain intervals whether the measuring signal of the displacement sensor is correct. In an assumed end position R1, R2, the opening spring or closing spring 12, 10 tries to accelerate the rotor shaft by means of the stored spring force when the rotor shaft moves away from the respective end position during full stroke. By a slow controlled method (moving, in particular forward and backward) of the rotor near the respective metastable torque neutral position R1, R2 of the full stroke can be at the self-adjusting current values for the current consumption of the electric motor 4, the actual moment zero point, the originally by way sensor per default predetermined distance can deviate defined zero, can be found. By determining the current minimum during the controlled rotor movement for the purpose of the displacement sensor calibration, the actual torque-neutral position can be determined.

In a second possible embodiment of the invention, the calibration of the displacement sensor takes place in that the rotor is controlled by selective control of the electric motor 4 via the control device 20 or another control or control unit in a between the two metastable torque-neutral positions or end positions (R1, R2; E2) located torque-neutral stable intermediate position RO is transferred and the assumed intermediate position RO serves as NuIIabgleich (or as a calibration point) for the calibration of the displacement sensor.

However, this displacement sensor calibration is only suitable for calibration during (low) speeds of the engine to be controlled in which a sufficient residence time of the rotor is guaranteed in the end positions R1, R2, since only during the Dwell time of the rotor in the moment-neutral end positions R1, R2, the rotor can be moved as described for the purpose of calibration. At high speeds, the rotor usually does not reach the torque-neutral end positions, so that such a calibration is not possible here. A movement or process of the rotor in the intermediate position is not required, since this position, in contrast to the metastable positions R1, R2 is unambiguously defined and thus checked directly based on the assumed stable center position RO position sensor and possibly corrected ,

Finally, a fault detection is provided in a possible development of the invention. The error detection is carried out in a simple manner by the distances or rotor angle ranges between the torque-neutral positions R1, R2, RO or between a fixed reference point and one or more of the torque-neutral positions with a reference distance or reference angle range is compared and in deviation by a predetermined value an error signal is generated.

Claims

claims

1. A method for calibrating a displacement 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 in opposite directions of drive to the gas exchange valve (2) acting energy storage means (10, 12),

- And a control unit for controlling the electric motor (4) such that the gas exchange valve (2) from a first end position (E1), in which via the rotor of the electric motor (4) driven actuator (6, 6a, 6b) and thus also the rotor is in a metastable torque-neutral position (R1) assigned to the first end position (E1), into a second end position (E2), in which the actuating element (6, 6a, 6b) or the rotor is in a second end position (E1). E2), and vice versa, characterized in that, starting from a moment-neutral position (R1; R2), the electric motor (4) is driven in such a way that the rotor extends by a distance in at least one direction the moment-neutral position (R1, R2) is moved out,

- the resulting current consumption of the electric motor (4) is detected,

- and depending on the self-adjusting current values for the current consumption of the electric motor, a new rotor position (R1 *, R2 ^* ) for calibration of the displacement sensor is determined.

2. The method according to claim 1, characterized in that the rotor in both directions from its moment-neutral position (R1, R2) is moved by a distance and in dependence on the self-adjusting current values for the current consumption of the electric motor, a new torque-neutral position (R1 * , R2 *) is determined.

3. A method for calibrating a displacement sensor of a Drehaktuatorvorrichtung for driving a gas exchange valve of an internal combustion engine, wherein the Drehaktuatorvorrichtung comprises:

- And a control unit for controlling the electric motor (4) such that the gas exchange valve (2) from a first end position (E1), in which via the rotor of the electric motor (4) driven actuator (6, 6a, 6b) and thus also the rotor is in a metastable torque-neutral position (R1) assigned to the first end position (E1), into a second end position (E2), in which the actuating element (6, 6a, 6b) or the rotor is in a second end position (E1). E2) assigned metastable torque-neutral position (R2), is transferred and vice versa, characterized in that

- The electric motor (4) is driven such that the rotor or the actuating element (6, 6a, 6b) in a between the two metastable month-neutral positions or end positions (R1, R2; E1, E2) located torque-neutral stable intermediate position RO is transferred and takes place based on the assumed stable intermediate position RO calibration of the displacement sensor.

4. The method according to one or more of the preceding claims, characterized in that the distance or the rotor angle between at least two torque-neutral positions (RO, R1, R2) of the rotor or between a fixed reference point and a metastable torque-neutral position of the rotor (R1, R2) is monitored and in case of deviation by a predetermined value from a predetermined reference value, an error signal is generated.