DE102004027966B4 - Method and apparatus for operating an actuator operating a switching cam device - Google Patents

Abstract

A method of operating an actuator (1) which actuates a switching cam device (6) of a camshaft (6a) driven by a crankshaft of an internal combustion engine for switching a valve lift, characterized in that a driving time of the actuator (1) for switching between a switching cam device ( 6) releasing state and the switching cam device (6) actuated state of the actuator (1) is set depending on operating conditions of the actuator (1), wherein the setting of the drive timing with respect to a change of the operating conditions dependent on the flight time with the switching cam device (6) in operative connection reaching adjusting element (2) of the actuator (1).

Description

The invention relates to a method and a device for operating an actuator which actuates a switching cam device, according to the preamble of claim 1 and the preamble of claim 10.

It is known to reduce the fuel consumption and the pollutant emission valve timing and valve lift characteristics in response to engine operating conditions of an internal combustion engine. For example, in a camshaft driven by a crankshaft of the internal combustion engine, it is known to switch from a first cam lift of a cam for the lower speed range to a second cam lift of a cam for the upper speed range of the internal combustion engine. For this purpose, an actuator causes an axial displacement of one or more cams on the camshaft. Such a device is from the DE 100 33 437 A1 known.

The publication DE 198 33 621 A1 describes a valve control for internal combustion engines with at least two different valve times, wherein each valve is associated with at least two cam tracks arranged side by side cam package, which is arranged to be non-rotatably but axially displaceable on a camshaft, and in the axial adjustment of the cam packages, each cam package one Number radially adjustable to the camshaft and associated with one in each of two arranged on each cam package radial link plates and over a portion of the disc circumference sufficient gate track cooperating, spring-loaded actuating pin and a locking bolt is assigned, being provided to avoid switching errors, that the enforcement a displacement movement of the individual cam packs in response to a rotational movement of the camshaft associated actuating bolt by means of a in dependence Wä hlbarer operating parameters of the internal combustion engine controllable actuator driven actuator can be locked in an inoperative retracted position.

Furthermore, from the document DE 102 11 395 A1 an actuating means for a switchable valve train of an internal combustion engine, which is engageable with a slot-like spiral groove of a cam piece to the axial displacement, which cam piece at least two juxtaposed lifting cams of different course, said actuating means of a housing, a telescopically projecting from this pin for a direct engagement in the spiral groove, a mechanical spring means acting on the bolt and an externally controllable displacement means for the bolt. According to the invention, the displacement means is designed as a permanent-electro-magnet, which holds the bolt in the de-energized state out of engagement with the spiral groove, wherein the spring means acts on the bolt in the direction of the spiral groove. As a result, a very quick and secure engagement of the bolt is made in the corresponding spiral groove.

The object of the invention is to provide a method and a device for operating an actuator, with which a valve switching is improved.

According to the invention the object is solved by the features of independent claim 1 and independent claim 10, advantageous embodiments of the invention describe the dependent claims.

The inventive method provides in addition to the generic features that a driving time of the actuator for switching between a switching cam device releasing state and the Umschaltnockenvorrichtung actuated state of the actuator is set depending on operating conditions of the actuator. This ensures a reliable switching of the Umschaltnockenvorrichtung despite a dependent of operating conditions of the actuator switching speed. In particular, an acceleration or a slowing down of the extension of an adjusting element of the actuator can be compensated. Advantageously, as far as possible influencing variables which have an influence on a switching behavior and in particular a time behavior of a control in a drive means of the actuator are compensated.

Preferably, the drive time is selected so that an adjusting element of the actuator which actively engages with the switching cam device always comes into operative connection with the switching cam device in a defined control window. The actuation time in which the actuator is actuated so that its adjusting element is extended in a control window, in particular related to a defined crank angle. If, for example, the adjusting element engages in a spiral groove of a switching cam in order to displace it axially for switching over to the camshaft, a displacement of the switching cam is possible only in a base circle of the cam contour, wherein the preferred embodiment ensures that a displacement can only be achieved if the assignment is defined Shifting to a crankshaft position and / or a camshaft position is possible. Appropriately, therefore, is the control window tied to the defined crankshaft position and / or the defined camshaft position. Preferably, the adjusting element is fully extended in a defined interval of the driving window and in operative connection with the switching cam device. In particular, the drive time is the sum of dead time and time of flight of the adjustment and corresponds in particular to the beginning of the energization of the actuator until the adjustment is fully extended.

Conveniently, the drive window is between an opening time and a closing time of an engine intake valve relative to a crank angle, so that the adjusting element for an adjustment of the Umschaltnockenvorrichtung is brought into operative connection exactly in a desired crank angle range of the drive window with the Umschaltnockenvorrichtung. With different geometries, the person skilled in the art can select other, meaningful assignments of the control window.

According to the invention, the setting of the activation time point takes place with regard to a change in a time dependent on the operating conditions of a moving with the switching cam device in operative connection adjusting element of the actuator. It is favorable if, with an increase of an operating voltage of the actuator, the actuation time is set with regard to the reduced time of flight and / or with decreasing temperature of the actuator the actuation time with respect to the extended time of flight. Correspondingly, when the operating voltage of the actuator decreases, the activation time with regard to the extended flight time and / or with increasing temperature of the actuator with regard to the shortened flight time can be set. Furthermore, it is favorable if the actuation time is set as a function of aging effects in the actuator and / or the actuation time is set as a function of an engine speed and / or an engine speed change of the internal combustion engine.

In a device according to the invention, it is proposed that a drive means is provided for setting a triggering instant of the actuator, at which the actuator can be switched between a state releasing the switching cam device and a state of the actuator actuating the switching cam device, depending on operating conditions of the actuator. Preferably, at least one temperature of the actuator and / or an operating voltage of the actuator can be determined.

• 1 schematisch eine Vorrichtung mit einem Aktor zur Betätigung einer Umschaltnockenvorrichtung als Schnitt;
• 2 einen funktionalen Zusammenhang zwischen Ventilhub, axialer Verschiebung der Umschaltnockenvorrichtung und Nuttiefe mit einem Kurbelwellenwinkel.

Other embodiments, aspects, and advantages of the invention are to be had in light of the summary thereof in the claims without limiting the generality of the following detailed representation with reference to drawings. Showing:

• 1 schematically a device with an actuator for actuating a Umschaltnockenvorrichtung as a section;
• 2 a functional relationship between valve lift, axial displacement of Umschaltnockenvorrichtung and groove depth with a crankshaft angle.

In 1 is a device with an actuator 1 for actuating a switching cam device 6 shown in section. In a preferably metallic housing 5 of the actor 1 is designed as a pin adjustment 2 movable up and down. In its center, the adjusting element 2 designed as a web permanent magnet 3 on. One end of the adjusting element 2 protrudes into a coil 4 , which by means of a power supply 8th can be energized and the adjustment 2 can attract or repel. The adjusting element 2 is shown in its retracted state with a solid line in its extended state is the adjusting element 2 shown in dashed lines. When retracted, the adjustment is 2 not with a switching cam device 6 in operative connection, in the extended state of the adjusting element 2 stand this and the switching cam device 6 so operatively connected that the switching cam device 6 on a camshaft, shown in cross-section 6a axially displaceable (perpendicular to the image plane). The permanent magnet 3 ensures a stable position of the adjusting element 2 in the retracted and extended state, by this in the extended state on the housing 5 and strikes in the retracted state at an unspecified stop in the housing.

The switching cam device 6 has a cam piece with a spiral groove 9 on, in which the designed as a pin adjustment 2 for shifting the switching cam device 6 engages in its extended state and in the spiral groove 9 moves along while the cam piece on the camshaft 6a is moved. Is the actor 1 fully extended, is the adjustment 2 in its extended state and reaches into the spiral groove 9 one. The cam piece carries different cam contours, for example a first cam contour for a large valve lift and a second cam contour for a small valve lift. While the cam piece on the camshaft 6a is shifted, for example, an unillustrated gas inlet valve or gas outlet valve of an internal combustion engine is operated with the cam contour corresponding first or second valve lift.

The actuator is with a drive means 7 connected, the one driving time of the actuator 1 . where the actor 1 between a switching cam device 6 releasing state and a switching cam device 6 actuating state of the actuator 1 switchable, depending on operating conditions of the actuator 1 established. The driving means 7 can be integrated in a conventional engine control unit.

2 shows a functional relationship between a plotted on the ordinate first and second valve lift 12 . 16 , a depth profile 10 a spiral groove 9 and a plotted on the abscissa crankshaft angle KW of the device 1 , A control window 13 is between a time when an intake valve is opened and a time when the intake valve is closed. The actor 1 or its adjusting element 2 is energized at a drive time, and the adjustment 2 must be within the control window 13 in the extended state. The control time is chosen so that a dead time and a time of flight of the adjustment 2 be considered or compensated. A depth course 10 the spiral groove 9 shows a trough-shaped course with a flat bottom, corresponding to an observed deflection of the adjusting element 2 when extending out of the housing 5 , wherein a first valve lift 12 in the front part of the depth profile 10 occurred. As a dashed curve is the way 17 of the adjusting element 2 drawn from the retracted position to its extended position. In the further course of the spiral groove 9 or the depth profile 10 is at the end of the drive window 13 an axial displacement 11 to watch as soon as the adjusting element 2 has traveled its flight time from the retracted state to the extended state and is in the extended state. Up to a point A is the first valve lift 12 effective, from a point B is the second valve lift 16 effective. Between the points A and B switching takes place between the two valve lifts associated cam contours by the Umschaltnockenvorrichtung 6 is moved axially. An interval 18 indicates the area in which the adjustment element 2 must be extended to the spiral groove 9 intervene. The activation time is correspondingly earlier, to dead times and the time of flight of the adjustment 2 to compensate. For the axial displacement 11 is the actuator 1 or its adjusting element 2 exactly in the crank angle range of the control window 13 in the extended state.

The inventive method provides that the drive time of the actuator 1 for switching between a switching cam device 6 releasing state and a switching cam device 6 actuating state of the actuator 1 depending on operating conditions of the actuator 1 is set. The drive timing is selected so early that one with the switching cam device 6 in operative connection reaching adjusting 2 of the actor 1 always in a defined interval 18 of the drive window 13 with the switching cam device 6 in active connection device.

Preferably, the control window is bound to a defined crankshaft position corresponding to a crank angle and / or a defined camshaft position, wherein the position of the drive window is geometrieabhängig. Appropriately, the control window is between an opening time and a closing time 15 an intake valve based on a crank angle of the crankshaft. The activation time results as the sum of the dead time and the time of flight of the adjusting element 2 , In particular, the duration is taken into account in the activation time from the time at which the current supply of the actuator or its coil 4 begins until the adjusting element 2 of the actor 1 fully extended.

The setting of the driving timing is made with respect to a change in a flying time of one with the switching cam device 6 in operative connection reaching adjusting element 2 of the actor 1 , The flight time of the adjustment element 2 ie the time that the adjusting element 2 required to move from its retracted position to the extended position when switched depends on different operating conditions such as temperature, applied voltage, pollution and the like. Furthermore, the exceeded crank angle range is dependent on the rotational speed of the internal combustion engine.

Preferably, upon an increase in an operating voltage of the actuator 1 the activation time set in terms of reduced flight time. If the operating voltage drops, the activation time is set with regard to an extended flight time. It is also favorable, with decreasing temperature of the actuator 1 to set the activation time with regard to the extended flight time and vice versa, to consider a shortened flight time with increasing temperature. Furthermore, the activation time may depend on aging effects in the actuator 1 and / or be adjusted depending on an engine speed and / or an engine speed change of the internal combustion engine.

The applied voltage at the actuator 1 is from the driving means 7 or the engine control unit known. If the voltage increases, the flight time is reduced. The temperature of the actuator 1 can via a temperature model in the drive means 7 or modeled in the engine control unit, for example as a function of the engine temperature, the driving time and the like. Because the actor 1 or its adjusting element 2 running in oil, the temperature has an influence on the friction of the adjusting element 2 and thus on the flight time. If the temperature drops, the flying time increases. Likewise, runtime effects and aging have an impact on flight time and vice versa. With increasing use, the oil quality decreases due to contamination, so that the time of flight increases due to the influence of friction. This effect can be recorded via maintenance intervals. If the internal combustion engine is not in a stationary state, then the size of the exceeded crank angle range increases or decreases depending on the activation of the engine up to the extended state.

LIST OF REFERENCE NUMBERS

1

actuator

2

adjustment

3

permanent magnet

4

Kitchen sink

5

casing

6

Umschaltnockenvorrichtung

6a

camshaft

7

driving means

8th

power supply

9

spiral

10

Depth gradient spiral groove

11

axial displacement

12

first valve lift

13

Ansteuerfenster

16

second valve lift

17

Way of adjusting element

18

interval

Claims (10)

A method of operating an actuator (1) which actuates a switching cam device (6) of a camshaft (6a) driven by a crankshaft of an internal combustion engine for switching a valve lift, characterized in that a driving time of the actuator (1) for switching between a switching cam device ( 6) releasing state and the switching cam device (6) actuated state of the actuator (1) is set depending on operating conditions of the actuator (1), wherein the setting of the drive timing with respect to a change of the operating conditions dependent on the flight time with the switching cam device (6) in operative connection reaching adjusting element (2) of the actuator (1). Method according to Claim 1 , Characterized in that the drive timing is chosen so that with the Umschaltnockenvorrichtung (6) coming into operative connection adjusting element (2) of the actuator (1) always falls into a defined Ansteuerfenster (13) with the Umschaltnockenvorrichtung (6) in operative connection. Method according to Claim 2 , characterized in that the control window (13) is bound to a defined crankshaft position and / or a defined camshaft position. Method according to Claim 1 . 2 or 3 , characterized in that is set at a rise in an operating voltage of the actuator (1) of the drive timing with respect to the reduced flight time. Method according to Claim 1 . 2 . 3 or 4 , characterized in that is set at a decrease in an operating voltage of the actuator (1) of the driving time with respect to the increasing flight time. Method according to one of Claims 1 to 5 , characterized in that when the temperature of the actuator (1) of the driving time is set with respect to the extended flight time. Method according to one of Claims 1 to 6 , characterized in that with increasing temperature of the actuator (1) the driving time is set with regard to the shortened flight time. Method according to one of Claims 1 to 7 , characterized in that the activation time is set depending on aging effects in the actuator (1). Method according to one of Claims 1 to 8th , characterized in that the drive timing is adjusted depending on an engine speed and / or an engine speed change of the internal combustion engine Device for operating an actuator (1), with which a switching cam device (6) of a crankshaft of an internal combustion engine driven camshaft (6a) for switching a valve lift is actuated, characterized in that a drive means (7) is provided to a driving time of the Actuator (1) on which the actuator (1) between a the switching cam device (6) releasing state and the switching cam device (6) actuated state of the actuator (1) is switchable, depending on operating conditions of the actuator (1) set, the Setting the activation time with respect to a change of a dependent on the operating conditions flight time with the Switching cam device (6) takes place in operative connection adjusting element (2) of the actuator (1).

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