DE102017125909A1 - An electric camshaft adjuster for variable valve timing of an internal combustion engine, method for operating an electric camshaft adjuster and use of an electric motor in an electric camshaft adjuster - Google Patents

Abstract

The invention relates to a method for operating an electric camshaft adjuster for variable valve control of an internal combustion engine having an electric motor (1) for generating a torque for adjusting the relative phase position of a camshaft (3) relative to a crankshaft of the internal combustion engine, characterized in that to increase the adjustment speed ( ΔV _max , ΔN _max ) when adjusting in the direction of rotation of the crankshaft, the electric motor (1) is operated with a predetermined pre-commutation. The invention further relates to an electric camshaft adjuster and a use of an electric motor in an electric camshaft adjuster.

Description

Field of the invention

The invention relates to a method for operating an electric camshaft adjuster for variable valve timing of an internal combustion engine, an electric camshaft adjuster and a use of an electric motor in an electric camshaft adjuster according to the closer defined in the preamble of patent claims 1, 3 and 5, respectively.

Out DE 10 2008 059 005 A1 an adjusting device for adjusting a relative angular position of two shafts with an adjusting gear is known, which has a non-rotatably connected to a Verstellmotorwelle an electric adjusting motor adjusting shaft. A disadvantage of this embodiment, the fact that at higher speeds of the crankshaft, the adjustment speed drops to a critical range, which can cause problems during operation.

Summary of the invention

The invention is therefore an object of the invention to provide a camshaft adjuster, a method and a use of the aforementioned type, which improve the performance of the camshaft adjuster with simple means.

The object is solved by the features of patent claim 1 and alternatively by the features of patent claims 3 and 5. Further advantageous embodiments will become apparent from the respective dependent claims, the description and the drawings.

A method is proposed for operating an electric camshaft adjuster for variable valve control of an internal combustion engine having an electric motor for generating a torque for adjusting the relative phase position of a camshaft relative to a crankshaft of the internal combustion engine. Since the adjustment of the relative phase in the direction of rotation of the crankshaft, the electric motor is operated with a predetermined pre-commutation, in the critical range at higher speeds of the crankshaft at a given speed and torque of the electric motor, the adjustment of the camshaft adjuster can be increased in the critical range in a simple manner.

Preferably, when adjusting the relative phase position in the direction of rotation of the camshaft and a rotational speed of a drivable by the crankshaft drive wheel of the camshaft adjuster greater than 3000 revolutions per minute reaches a maximum displacement greater than 200 ° per second based on the rotational angle of the camshaft. Taking into account the usual drive kinematics between the drive wheel and the crankshaft, this speed corresponds to a rotational speed of the latter of approximately 6000 revolutions per minute.

By varying all possible pre-commutation angles as a function of predetermined boundary conditions, an optimized pre-commutation angle for generating a maximum adjustment speed at a predetermined critical speed can be calculated model-based. In this case, the adjustment speeds are considered over all speeds and is in the critical range, i. in the range of lowest adjustment speed, this increases. To vary the Vorkommutierungswinkels particular boundary conditions can be considered in particular: the applied voltage, the current limit and the temperature of the electric motor, further to a standing on a traction drive in drive connection with the crankshaft drive wheel, in particular sprocket, the camshaft adjuster force, the friction behavior in the transmission , in particular the temperature and the transmission oil, the camshaft adjuster and the average friction torque acting on the camshaft as a function of the speed of the drive wheel of the camshaft adjuster and the temperature. Other aspects that affect the pre-commutation of the electric motor can also be taken into account, such as the torque of the electric motor during startup, adjustment speeds to other crankshaft speeds, and power consumption.

The critical speed of the camshaft adjuster is in the range of maximum crankshaft speed, preferably greater than 6000 rpm. Preferably, it is assumed that a critical adjustment speed of 200 ° per second, based on the angle of rotation of the camshaft.

Preferably, the electric motor is operated with a pre-commutation angle, which is electrically in the range of 30 ° to 60 ° so-called electrical angle. This is convertible into the angular position of the rotor of the electric motor via the number of pole pairs. In this way, an overload of the electrical circuit of the camshaft adjuster, in particular by excessive power consumption and occurrence of excessive reverse voltages, safely avoided.

It is also advantageous if a pulse-width-modulated control (PWM) of the electric motor takes place for sensor-controlled pre-commutation.

The object of the invention is also achieved by an electric camshaft adjuster for variable valve control of an internal combustion engine. The camshaft adjuster has an electric motor for generating a torque for adjusting the relative phase position of a camshaft relative to a crankshaft of the internal combustion engine. For sensor-controlled commutation several sensors are provided on the electric motor, which are arranged according to the invention in the circumferential direction opposite to a central axis located in a magnetically neutral area by a predetermined angle against the direction of rotation of the crankshaft. As a result, a pre-commutation of the electric motor is achieved, such that in the critical range at higher rotational speeds of the crankshaft, the maximum possible adjustment speed of the camshaft adjuster is increased.

The aforementioned angular offset can be achieved, for example, in a range of 7.5 ° to 15 °, whereby a pre-commutation angle of 30 ° to 60 ° can be achieved.

A simple sensor-controlled pre-commutation is possible in that a plurality of sensors are arranged on a stator of the electric motor for detecting the position of a radially enclosed rotor of the electric motor of the stator. The sensors are in the circumferential direction to a magnetically neutral center axis located between a plurality of Pohlschuhen distributed over the circumference of the stator by a predetermined angle opposite to the direction of rotation of the rotor, i. offset or offset from the direction of rotation of the crankshaft. Preferably, three digital Hall sensors are provided to distinguish six pre-commutation blocks.

Preferably, the sensors are arranged in a region opposite the Pohlschuhen axially upstream region. As a result, an offset or displacement of the sensors without limitation by Pohlschuhe possible.

The object of the invention is further achieved by a use of an electric motor in an electric camshaft adjuster for variable valve timing of an internal combustion engine, wherein the electric motor for generating a torque for adjusting the relative phase position of a camshaft relative to a crankshaft of the internal combustion engine is used. According to the invention, a pre-commutated electric motor is used to increase the adjustment speed of the camshaft adjuster in a predetermined higher speed range of the crankshaft.

list of figures

• 1 schematisch eine geschnittene Darstellung eines erfindungsgemäßen Nockenwellenverstellers ,
• 2 einen schematischen Querschnitt eines Elektromotors des Nockenwellenverstellers,
• 3 in einem Diagramm die Verstellgeschwindigkeit des Nockenwellenverstellers in Abhängigkeit von der Drehzahl eines Antriebsrads desselben,
• 4 in einem Diagramm das Drehmoment des Elektromotors in Abhängigkeit von der Drehzahl desselben.

Further features of the invention will become apparent from the following description and from the drawings, in which several embodiments of the invention are shown in simplified form. Show it:

• 1 1 is a schematic sectional view of a camshaft adjuster according to the invention;
• 2 a schematic cross section of an electric motor of the camshaft adjuster,
• 3 in a diagram, the adjustment speed of the camshaft adjuster in dependence on the rotational speed of a drive wheel thereof,
• 4 in a diagram, the torque of the electric motor in dependence on the speed of the same.

Detailed description of the drawings

1 schematically shows an electric camshaft adjuster according to the invention for variable valve timing of an internal combustion engine. The camshaft adjuster comprises an electric motor 1 and a gearbox 2 for generating and transmitting a torque to a camshaft 3 the internal combustion engine. The camshaft adjuster is used to adjust the relative phase angle of the camshaft 3 relative to a crankshaft, not shown, and variable control of the opening and closing times of at least one gas exchange valve, not shown, of the internal combustion engine. The gear 2 is of a drivably connected to the crankshaft drive wheel 4 radially outward, which is designed here as a sprocket of a chain drive connected to the crankshaft. It is also conceivable, the drive wheel 4 form as pulley of a belt drive. By energizing the electric motor 1 with a stator 5 is at one with a rotor of the electric motor 1 rotatably connected motor shaft 6 a torque can be generated as an adjusting torque via the transmission 2 on the camshaft 3 is transferable.

In 2 is the electric motor 1 with the one from the stator 4 radially outer rotor included 7 shown schematically. The stator 5 is with six evenly distributed over the circumference arranged Pohlschuhen 8th formed, wherein the current-supply windings are not shown. The Pohlschuhe 8th are spaced apart in the circumferential direction in each case by an air gap. For sensor-controlled commutation are three sensors 9 . 10 . 11 in each case in the air gaps between four in the circumferential direction successively arranged Pohlschuhen 8th arranged. The sensors 9 . 10 . 11 are as Hall Sensors executed. According to the of the sensors 9 . 10 . 11 delivered position information is energized by a power electronics, not shown, the energization of the windings, not shown, one after the other to the rotor 7 and with this rotatably connected motor shaft 6 a torque for adjusting the camshaft 3 produce.

Here is the direction of rotation of the rotor 7 for adjusting the cam adjuster in the direction of rotation of the crankshaft indicated by an arrow.

The sensors 9 . 10 . 11 are each on the stator with respect to a circumferentially centrally between the Pohlschuhen 8th located magnetically neutral area, passing through a central axis 12 is indicated by a predetermined angle α against the direction of rotation of the rotor 7 , which corresponds to the direction of rotation of the crankshaft, staggered.

The thus staggered arrangement of the sensors 9 . 10 . 11 serves to generate a predetermined Vorkommutierung upon adjustment of the cam timing in the direction of rotation of the crankshaft, ie in Vorwärtsverstellrichtung. Here, the commutation of the electric motor takes place 1 based on the direction of rotation of the rotor 7 earlier in time with respect to a normal commutation of the electric motor 1 , Thereby, a predetermined weakening of the permanent magnet of the electric motor 1 reached generated magnetic field. This is operated, for example, as a field-oriented controlled (FOC) permanent magnet synchronous motor. A shift of the sensors 9 . 10 . 11 in the opposite direction, ie in the direction of rotation of the rotor 7 leads to a late commutation of the electric motor 1 ,

The angular offset α is here preferably in a range of α = 7, 5 ° to α = 15 °. This can be a pre-commutation of the electric motor 1 be achieved with adjustment in the direction of rotation of the crankshaft with a Vorkommutierungswinkel in a range of 30 ° to 60 ° as a so-called electrical angle. With different pole pairs, different mechanical angles can be present even with the same electrical angle.

The adjustment speed of the camshaft adjuster describes the relative adjustment of the phase angle between the camshaft 3 and crankshaft per unit time. It can be based on the rotation of the crankshaft in degrees of rotation of the crankshaft per second [° Kw / s] or on the rotation of the camshaft 3 in degrees of rotation of the camshaft per second [° Nw / s] depending on the reference system. The adjustment speed between the camshaft 3 and crankshaft differs by the translation of the drive connection, here a traction drive designed as a chain drive. Under simplified assumption is the speed of the drive wheel 4 due to the kinematics of the traction drive half of the speed of the crankshaft. For example, the speed of the crankshaft is 100 ° / s and the speed of the drive wheel 4 , or the sprocket, 50 ° / s. About the drive wheel 4 and by the electric motor 1 becomes the speed of the camshaft 3 brought to 55 ° / s. As a result, the adjustment speed, depending on the reference system, is 5 ° Nw / s relative to the camshaft 3 or 10 ° Kw / s relative to the crankshaft.

3 shows in a diagram by the electric motor 1 can be generated maximum possible adjustment speed .DELTA.V _{max of} the camshaft adjuster based on the rotation of the camshaft 3 in degree of rotation of the camshaft 3 per second [° Nw / s] depending on the speed of the drive wheel 4 of the camshaft adjuster. There is the course of the maximum possible adjustment without Vorkommutierung the electric motor 1 in a curve ΔV _max1 shown. This increases with increasing speed of the drive wheel 4 linear and passes for higher speeds greater than 3000 U / min. in a critical range with the smallest adjustment speed, which is referred to as the critical adjustment speed. The speed of the drive wheel corresponds 4 the camshaft adjuster greater than 3000 U / min a speed of the crankshaft greater than 6000 rev / min. By pre-commutation of the electric motor, the maximum possible adjustment speed according to the curves ΔV _max2 and ΔV _max3 with a pre-commutation angle of 30 ° or 60 ° as so-called electrical angle of the electric motor 1 be increased significantly in the critical range at higher speeds. For higher speeds of the drive wheel 4 greater than or equal to 3000 rpm. becomes an adjustment speed ΔV _max2 and ΔV _max3 greater than 200 ° Nw / s achieved. The diagram 3 refers to a so-called positive gear. The invention pre-commutation of the electric motor 1 the camshaft adjuster is also applicable to so-called negative gear.

Furthermore, in the diagram according to 3 the course of the maximum possible adjustment speed in the negative direction of rotation of the drive wheel 4 applied. This course is to be regarded as uncritical, since the maximum possible adjustment thus increases the Verstellreserve in the negative direction of rotation with the speed and is greater in total compared to the positive direction of rotation.

The effects of Vorkommutierung in Vorwärtsverstellrichtung the cam phaser are still in the diagram according to 4 shown. There, the load is as generated mean torque in Nm as a function of the speed of the electric motor 1 in revolutions / minute in the curves 13 . 14 . 15 respectively for positive forward direction of rotation of the electric motor 1 , that is applied in the forward adjustment of the cam phaser. Depending on the positive or negative load, the speed of the electric motor 1 on. The characteristics 13 . 14 . 15 each mark the map at maximum possible voltage and PVM of the electric motor 1 in the positive forward direction of rotation and the other characteristics mark the map accordingly in the negative direction of rotation. This is achieved by bridging the power electronics with a maximum possible pulse width modulated drive (PWM) of a B6 bridge with mostly 95% On and 5% Off. With freely selectable PWM is that of the respective characteristic 13 . 14 . 15 included inner area possible.

The first characteristic 13 stands for a map without Vorkommutierung, ie without displacement of the sensors 9 . 10 . 11 from the middle position and without weakening the magnetic field, while the second and third characteristics 14 . 15 show the map at a Vorkommutierung invention in Vorwärtsverstellrichtung the cam adjuster with a Vorkommutierungswinkel 30 ° or 60 ° in angular degrees electrically. This applies accordingly to the characteristic curves with negative torque.

Due to the pre-commutation, the characteristic curve is given for a given load 14 . 15 shifted to higher speeds, ie by pre-commutation can be a higher speed of the electric motor 1 be achieved, as by the characteristic map of the characteristic 13 is specified at maximum applied voltage and maximum PWM.

In this way, a map of the electric motor results 1 that is for positive load versus the characteristic 13 widened without Vorkommutierung in the direction of higher speed and thus changed asymmetrically. In the diagram according to 4 is the maximum possible adjustment speed or so-called adjustment reserve of the camshaft adjuster as a speed difference ΔN _max = n _AR - _EM for given speed n _AR of the drive wheel 4 and maximum speed _EM of the electric motor 1 represented at the given load as a double arrow, the length of the speed difference n _AR - _EM corresponds to the corresponding path length on the abscissa of the diagram. The adjustment speed ΔN _max is on the electric motor 1 and has the unit [° degree E-motor / s]. Due to the pre-commutation, the load on the pre-commutated characteristic curves is given a positive load 14 . 15 related maximum possible adjustment speed ΔV _max2 and ΔV _max3 opposite to the characteristic curve 13 without pre-commutation maximum possible adjustment speed ΔV _max1 clearly increased.

To illustrate, the maximum possible adjustment speeds ΔN _max1 . ΔN _max2 . ΔN _max3 based on the characteristics 13 . 14 . 15 for example, for a typical load case selected with a positive torque 0.1 Nm of the electric motor 1 and at a speed n _AR of the drive wheel 4 With n _AR = 3500 rpm, the latter showing a crankshaft speed of 7000 rpm. equivalent. Each based on the characteristics with negative torque of 0.1 Nm or load of the electric motor 1 maximum possible adjustment speed is likewise represented by double arrows in an analogous manner.

The gear 2 of the camshaft adjuster is constructed as a so-called three-shaft gearbox with an oval rolling bearing ( 1 ). An inner ring 16 of the rolling bearing is radially inward for transmitting torque to the motor shaft 6 in drive connection and forms the outer diameter of an oval, in particular elliptical tread for the rolling elements 17 of the rolling bearing. This is radially outward from a flexible toothed ring 18 a so-called flex ring comprises. This is via an external toothing on the drive wheel 4 supported and engages in an internal toothing with the camshaft 3 rotatably connected output ring gear for transmitting torque. The oval bearing and the toothed ring 18 form a so-called wave gear. About the oval shape and the tooth number differences a translation is achieved at the wave gear.

LIST OF REFERENCE NUMBERS

1

electric motor

2

transmission

3

camshaft

4

drive wheel

5

stator

6

motor shaft

7

rotor

8th

Pohl Shoe

9

sensor

10

sensor

11

sensor

12

central axis

13

curve

14

curve

15

curve

16

inner ring

17

rolling elements

18

toothed ring

α

corner

ΔV _max1

adjustment

ΔV _max2

adjustment

ΔV _max3

adjustment

ΔN _max

adjustment

ΔN _max1

adjustment

ΔN _max2

adjustment

ΔN _max3

adjustment

n _AR

number of revolutions

_EM

number of revolutions

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 102008059005 A1 [0002]

Claims (5)

Method for operating an electric camshaft adjuster for variable valve control of an internal combustion engine having an electric motor (1) for generating a torque for adjusting the relative phase position of a camshaft (3) relative to a crankshaft of the internal combustion engine, characterized in that to increase the adjustment speed (ΔV _max , ΔN _max ) is operated with adjustment in the direction of rotation of the crankshaft of the electric motor (1) with a predetermined pre-commutation. Method according to Claim 1 , characterized in that at a speed of a drivable by the crankshaft drive wheel (4) of the camshaft adjuster greater than 3000 revolutions per minute, the maximum displacement ( _{.DELTA.V max2} , _{.DELTA.V max3} ) is greater than 200 ° per second based on the rotation angle of the camshaft (3 ). Electric camshaft adjuster for variable valve control of an internal combustion engine, having an electric motor (1) for generating a torque for adjusting the relative phase position of a camshaft (3) relative to a crankshaft of the internal combustion engine, characterized in that the sensor-controlled commutation electric motor (1) comprises a plurality of sensors (9 , 10, 11) which are offset in the circumferential direction from a central axis (12) located in a magnetically neutral region by a predetermined angle (a) counter to the direction of rotation of the crankshaft. Electric camshaft adjuster to Claim 3 , characterized in that the electric motor (1) has a plurality of distributed in the circumferential direction Pohlschuhe (8) and the sensors (9, 10, 11) are arranged in a relation to the Pohlschuhen (8) axially upstream region. Use of an electric motor (1) in an electric camshaft adjuster for the variable valve control of an internal combustion engine, for generating a torque for adjusting the relative phase position of a camshaft (3) relative to a crankshaft of the internal combustion engine, characterized in that to increase the adjustment speed of the camshaft adjuster at higher speeds Crankshaft of the electric motor (1) is vorkommutiert.

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