EP1642011A1

EP1642011A1 - Device and method for determining the angle of rotation of a camshaft in relation to the crankshaft of an internal combustion engine

Info

Publication number: EP1642011A1
Application number: EP04739675A
Authority: EP
Inventors: Jens Schäfer; Martin Steigerwald
Original assignee: Schaeffler KG
Current assignee: IHO Holding GmbH and Co KG
Priority date: 2003-07-09
Filing date: 2004-06-08
Publication date: 2006-04-05
Also published as: DE10330872B4; US7541803B2; DE10330872A1; US20070101956A1; WO2005012698A1

Abstract

The invention relates to a device and a method for determining the angle of rotation between a camshaft (5) and the crankshaft of an internal combustion engine, said device comprising a camshaft regulator provided with an electronic regulator, and means for determining the position of the angle of rotation of the camshaft (5) and the crankshaft. According to the invention, a crankshaft triggering wheel provided with reference and trigger marks is fixed to the crankshaft for determining the position of the angle of rotation of the crankshaft, and an electromechanical camshaft regulator is provided, comprising a triple shaft gearbox (1), the first shaft (3) thereof being connected to the crankshaft (5) in a rotationally fixed manner, the second shaft (4) thereof being connected to the crankshaft by means of a camshaft drive wheel (7), and the third shaft thereof, as the regulating shaft (6), being connected to a permanent magnet rotor (8) of a BLDC motor (2), said BLDC motor (2) comprising a stator (9) that is fixed to the housing and an electronic commutation that can be controlled by commutation signals which are used both for determining the position of the angle of rotation of the camshaft (5), and together with the signals of the crankshaft trigger wheel, for calculating the angle of rotation between the camshaft (5) and the crankshaft.

Description

Name of the invention

Device and method for determining the angle of rotation of a camshaft relative to the crankshaft of an internal combustion engine

description

Field of the Invention

The invention relates to a device and a method for determining the angle of rotation of a camshaft relative to the crankshaft of an internal combustion engine, in particular according to the preamble of patent claim 1.

Background of the Invention

A camshaft adjuster is used to exactly maintain a set angle curve for the adjustment angle of the camshaft. Due to disturbance variables such as fluctuations in the drive torque of the camshaft, there are deviations between the setpoint and actual angles in practical engine operation. Reducing these deviations can lead to a reduction in pollutant emissions and fuel consumption, an increase in engine output and torque, as well as a reduction in the electrical system load when the engine is started and the engine speed at low idle. It is particularly important to maintain the optimum adjustment angle when starting the engine in order to reduce the high level of raw emissions in this operating state. DE 43 17 527 A1 discloses a method for determining the angle of rotation ΔΦ of a camshaft relative to the crankshaft of an internal combustion engine, which has a hydraulic camshaft adjuster with an electronic see controller and means for determining the angular position of the camshaft relative to the crankshaft.

In this system, the speed and angle of rotation of the crankshaft and camshaft are recorded to regulate the angle of rotation ΔΦ of the camshaft. Trigger wheels are attached to the crankshaft and camshaft. One sensor each detects the respective reference and trigger marks, which are used in the electronic controller to determine the speed and angle of rotation of the shafts and to calculate the angle of rotation ΔΦ.

Disadvantages of this solution are the required effort and the inadequate accuracy of the signal acquisition as well as the relatively slow, inaccurate and inaccurate adjustment of the angle of rotation ΔΦ which is only possible in normal engine operation with hydraulic camshaft adjusters.

Object of the invention

The invention is therefore based on the object of creating a possibility of determining the angle of rotation ΔΦ between a camshaft and the crankshaft of an internal combustion engine with high speed and accuracy.

Summary of the invention

According to the invention, this object is achieved by the features of the device claim 1.

Compared to hydraulic camshaft adjusters, the electromechanical camshaft adjuster offers the advantage of quick and exact adjustment and fixing of the angle of rotation ΔΦ of the camshaft. This applies to the entire operating range of the internal combustion engine, including the starting phase. The BLDC motor works with electronic commutation, so that the friction and wear of brushes and commutator are eliminated. The low moment of inertia and the high torque of the permanent magnet rotor enable a high adjustment speed of the BLDC motor.

The electronic commutation takes place by means of commutation signals which are generated in sensors by the rotary movement of the permanent magnet rotor and processed in a commutation computer. A sensor is required for each of the three phases of the stator.

The commutation signals are also suitable for determining the angle of rotation of the camshaft and, together with the reference and Tπggermark signals of the crankshaft trigger wheel, for determining the angle of rotation ΔΦ of the camshaft. In this way, the trigger wheel of the camshaft and its sensor, which would otherwise be required, are unnecessary. This saves costs, installation space and weight.

Known Hall and reluctance sensors or optical, inductive or capacitive sensors can be used as sensors for generating the commutation signals.

The generation of the commutation signals by self-induction in the three phases of the stator is particularly advantageous. The consequent elimination of the sensors reduces the costs and the susceptibility to faults, in particular as a result of the high temperature of the BLDC motor.

The space requirement of the sensors and their construction costs are reduced by the fact that they can be installed in components of the BLDC motor that rotate at rotor speed, such as. B. bearing or sealing rings.

A trouble-free start and start-up of the internal combustion engine is ensured by the fact that a RAM or an EPROM is provided in a control unit or an active, storable Hall sensor which controls the counters and thus the Save or make recognizable the position of the camshaft at standstill or when starting the internal combustion engine.

The active Hall sensors already react to the north or south pole when voltage is applied and thus detect the position of the camshaft immediately after the ignition lock is actuated or when the internal combustion engine is started. In this way, the target adjustment position can also be adjusted or held during the starting process of the internal combustion engine.

The counter data stored in the memories enable the position of the camshaft to be recognized and corrected even when the engine is at a standstill. In both cases, fuel consumption and pollutant emissions are minimized in the critical starting phase.

In general, the angular position information is lost when the internal combustion engine is switched off. Then the rotor must be synchronized to the crankshaft again when the engine is started. If the crankshaft sensor registers an uniquely identifiable event, for example a missing tooth on the starter ring gear, the position of the crankshaft at a fixed reference point, for example at top dead center of the first cylinder, is recognized. If a tooth of the trigger wheel of the camshaft passes the camshaft sensor, the position of the camshaft relative to a cam, for example the maximum stroke of the first cam, is clearly recognized. The angular position of the camshaft relative to the crankshaft can be determined from the elapsed time between the event "missing tooth on crankshaft" and the event "trigger wheel tooth camshaft passes camshaft sensor". The control unit determines the elapsed time from the set "time stamps" for the events. The time stamps are set or generated using a high-frequency oscillating crystal. At this point in time, the rotor position can be clearly determined using the basic gear equation.

A second type of synchronization can be achieved by moving the stage to the mechanical end stop. If this position is reached, the position of the camshaft is relative to the crankshaft and thus the rotor position is also known from the three-shaft equation. This even works without a camshaft sensor. A disadvantage of this type of synchronization is the influence of the timing drive expansion due to temperature changes and / or aging of the belt or elongation of the timing chain on the accuracy of the detection of the camshaft position.

It may be that a so-called resolver or a component with the same function as the resolver is attached to the KW instead of the ring gear. In principle, the resolver is a high-resolution encoder that enables the crankshaft signal to be measured at an angle or speed.

Instead of the three Hall sensors or the alternative sensors mentioned, a resolver can be used as the basis for commutating the BLDC motor. During one revolution of the rotor, this can not only achieve a signal frequency of 'number of Hall sensors x number of poles' but a significantly higher resolution. The resolver function can equally be integrated into the "sensor bearing" or "sensor sealing ring" components already mentioned.

The object of the invention is also achieved by the features of method claim 5. The additive and multiplicative combination of the commutation and trigger signals offers an uncomplicated way of calculating the angle of rotation ΔΦ.

An advantageous embodiment of the invention consists in that the twist angle Δ wird is calculated on the basis of the following counter-based relationship: A number Hall signal 360

ΔΦ x- A number M gnapok

Where: _H aiisignaie number = number of signals of a Hall sensor, the signals of all the Hall sensors and the number of Hall sensors is derived from the quotient of the number Number _M agnetpoie = number of magnetic poles of the permanent magnet rotor;

Number _R eferenzmarke = number of the reference marks of the Kurbelwellentriggerrads;

Total number _T rigger = number of trigger marks on the Kurbelwellentriggerrad;

Number of triggers = number of trigger marks counted since the last reference mark;

i = gear ratio between the adjusting shaft and camshaft with the sprocket locked.

It is advantageous that the trigger mark signals determined after passing through a reference mark are deleted after the next reference mark has been reached. This prevents adjustment errors due to counter errors. It also limits the amount of memory required.

An advantageous further development of the invention consists in that a change in the direction of rotation of the BLDC motor is determined by evaluating the change in the commutation signals which occurs, for which purpose these are differentiated and the differential of the commutation signals of one of the three Hall sensors with the status (high / low) of the differentials Commutation signals from the other two Hall sensors is combined. In this way, a change in the direction of rotation is recognized by appropriate software.

The time-based determination of the twist angle ΔΦ according to the relationship. , ( ^■ (n ™ - - 2 - n ™), ΔΦ = \ ^ x dt ^J i requires considerably less storage space than the counter-based one.

Another advantage for a quick and exact calculation of the angle of rotation ΔΦ is that the counter and the time-based determination of the angle of rotation ΔΦ can be combined. Because the camshaft approaches a reference position, for example a base position with a mechanical stop, at counter and time-based determination of the twist angle ΔΦ or synchronizes itself to an edge of the camshaft trigger wheel in order to zero the counters, an exact calculation of the twist angle ΔΦ is achieved ensured with reduced memory size.

A saving of memory space and computer capacity is also achieved by determining the phase relationship of the camshaft to the crankshaft by evaluating the difference between these signals in a position controller, which preferably works with the camshaft or crankshaft speed applied, with an integral ratio of the crankshaft signals to at least one sensor signal of the adjusting shaft. As long as there is no adjustment on the variable speed gear unit, it rotates as a whole, so that the speed difference must be zero. If the adjustment mechanism is used for adjustment, there is a difference between the adjustment shaft signals and the crankshaft signals. Since the gearbox is fixed in its translations, each signal difference can be assigned a unique phase position of the camshaft. Working with the signal difference therefore requires less storage capacity and computing power instead of the sum of the individual signals. In addition to increasing the resolution of the phase position or to check the plausibility of the phase position, the camshaft signal can be recorded and processed by calculation.

It is also advantageous that the camshaft can be adjusted to any desired position after the ignition has been switched off and the internal combustion engine has stopped by a trailing BLDC engine or by a control unit overrun. In this way, there is no time loss when starting the desired rotation angle Δ An of the camshaft when the engine is started, so that an immediate start with the optimal rotation angle ΔΦ is ensured. Brief description of the drawing

Further features of the invention result from the following description and the drawing, in which an embodiment of the invention is shown schematically.

The drawing shows an electromechanical camshaft adjuster with an adjusting gear designed as a three-shaft gear and an electric adjusting motor.

Detailed description of the drawing

The single drawing shows the basic structure of an electromechanical camshaft adjuster, in which the solution according to the invention is used.

The camshaft 5 is connected to a crankshaft (not shown) via a three-shaft adjustment gear 1. The first shaft 3 of the adjustment gear 1 is connected to the camshaft 5 in a rotationally fixed manner, the second shaft 4 via a camshaft drive wheel 7 by means of a chain or toothed belt to the crankshaft and as a third Shaft an adjusting shaft 6 with a permanent magnet rotor 8 of an adjusting motor designed as a BLDC motor 2 (brushless direct current motor). A stator 9 of the same is firmly connected to a housing 10 of the internal combustion engine. The stator is three-phase.

The BLDC motor 2 is electronically commutated via commutation signals. The commutation signals are formed by the rotary movement of the permanent magnet rotor 8 in three Hall sensors, which are assigned to the three phases of the stator 9.

The permanent magnet rotor 8 is magnetized multipole on the circumference. With each revolution, a bipolar Hall sensor outputs one signal per pole, ie at one eight-pole magnet eight signals. With unipolar Hall sensors, only half the number of signals is output.

Since the camshaft 5 is in direct connection with the BLDC motor 2 via the three-shaft gearbox 1, the position of the camshaft 5 with the Hall sensors or their commutation signals can be determined as follows:

The basic speed equation of a three-shaft gearbox is as follows: nvw - n _NW xi + n _chain X (i - 1) = 0 (1) where n _NW = camshaft speed 5 nκeite = camshaft drive wheel speed 7 n = adjusting shaft speed 6 i = gear ratio.

Expressed in angles: Φv - ΦNW X! + Φchain X (i - 1) = 0 (2) with: Φ _NW = angle of camshaft 5; Φ _Ke tte = traveled angle of camshaft drive wheel 7; Φvw = angle of adjustment shaft 6.

The following applies to the adjustment angle:

ΔΦ = Φκ _e tte - Φ camshaft (3)

(2) in (3) yields:

ΔΦ = (Φ _Ke tte - Φvw) - i (4)

The following applies to the angles covered by the individual shafts: Φ = U x 360 ° (5) with: U = number of revolutions of the respective shaft.

(5) in (4) gives:

ΔΦ = (U _K ette - UVW) x 360 ° + i (6)

The number of revolutions of the variable motor can be calculated directly from the number of Hall signals from a Hall sensor as follows:

, , _ Anza l-wi-ign ..., - ,. Uvw ~ - (') Anza l Magnapol--

The number of Hall signals results from the quotient of the number of signals from all Hall sensors and the number of Hall sensors.

To identify cylinder 1, there is a reference mark on a crankshaft trigger wheel, not shown, with which the number of revolutions of camshaft drive wheel 7 can be determined:

A ΔntTz7aQlhlllητnggeι U chain - number of references mar e + - + 2 (8) total number πngger j with:

Total-rrigge. = Number of trigger marks on the crankshaft trigger wheel number τ _r igger = number of determined trigger marks since the last reference mark.

The number of determined trigger marks is reset after a new reference mark is reached.

With (7) and (8) in (6) the adjustment angle ΔΦ can be determined directly from the number of Hall signals and the number of reference and trigger mark signals of the crankshaft trigger wheel: -AjlNumber H-lIsignalc 360 ^c

ΔΦ = number-ME -, * A count rftramma <c + ^■ ^• 5- 2 - total number-m number-r numberM-g apoic (9)

To regulate the angle of rotation ΔΦ, both the Hall signals of the BLDC motor 2 and the reference and trigger mark signals of the crankshaft trigger wheel are added up. The current position of the camshaft 5 can thus always be determined using equation (9).

In order to avoid that there are adjustment errors due to counting errors, the camshaft 5 is moved into a reference position, e.g. B. moved to a basic position with a mechanical stop, zeroed the counter and started adding again. Although very large numbers are expected from the incrementing, the zeroing saves storage spaces.

The direction of rotation of the BLDC motor is also determined via the Hall sensors, since this can change depending on the direction of adjustment. In this case, the Hall signals are subtracted from the counter.

The direction of rotation can be determined by evaluating the sequence of the signals from the three Hall sensors. Detection is possible whenever one of the Hall signals changes. In order to recognize this, the signals of the Hall sensors ABC are differentiated. The direction of rotation can be determined if the differential is combined with the status (high / low) of another signal.

When the internal combustion engine is switched off, the counters are stored in a RAM or EPROM of the control unit, so that when the engine is started, the position of the camshaft is immediately known. Furthermore, it is advantageous to use active, storable Hall sensors that react to the north or south pole even when voltage is applied. Since the position of the camshaft 5 is recognized immediately after the ignition lock has been actuated or when the crankshaft and camshaft 5 start to rotate, in particular when an active, storable Hall sensor is used, the desired adjustment position can also be adjusted and held during the starting process of the internal combustion engine. This is advantageous because of the associated reduction in fuel consumption and exhaust gas emissions. Any desired adjustment position can also be approached to the same extent when the vehicle is parked after turning the ignition key. This is achieved by an active overrun of the BLDC motor 2 or the control unit. It is advantageous here to avoid wasting time when approaching the desired angle of rotation when starting the engine.

Since a lot of memory space is required for the counter-based variant of the rotation angle determination described above, a variant is described below which is based on a time-based determination of the rotation angle.

In the time-based variant, the angle of rotation is determined via the speed difference between the crankshaft and adjusting shaft 6.

The speed of the crankshaft is determined by determining the time that elapses between two or more crankshaft trigger marks. Since the trigger marks have a fixed angle to each other, the speed results: n «W ⁼ ΔΦ-rig marks + Δt with: n _K w = crankshaft speed; Φγ _r igge _rm a _rk e _n = angle between two or more crankshaft trigger marks;

Δt = time that passes between two or more trigger marks.

The speed of the BLDC motor 2 can be determined by the time that passes between two or more signals on the adjusting shaft. nw = ΔΦ _Ma gπetpole (Δt 'X k) With:

ΔΦMagnet oie = angle between two magnetic poles;

Δt '= time that elapses between two signals on the adjusting shaft;

K = constant, which contains the number of sensor signals between two magnetic poles.

The adjustment angle can be determined as follows:

Approaching a reference mark to zero the system is also conceivable for the time-based determination of the angle of rotation. However, it is also conceivable that the synchronization between the crankshaft, the adjusting shaft and the camshaft takes place in the manner already described above. A combination of counter and time-based determination of the angle of rotation is also possible.

LIST OF REFERENCE NUMBERS

Three-shaft transmission

BLDC motor

First wave

Second wave

camshaft

adjusting

camshaft drive wheel

Permanent magnet rotor

stator

casing

Claims

claims

1. Device for determining the angle of rotation ΔΦ between two shafts, in particular between a camshaft (5) and the crankshaft of an internal combustion engine, which has a camshaft adjuster with an electronic controller and means for determining the angle of rotation of the camshaft (5) and the crankshaft, characterized in that a crankshaft trigger wheel with reference and trigger marks is attached to the crankshaft to determine the angular position of the crankshaft, and in that an electromechanical camshaft adjuster is provided which has a three-shaft gearbox (1), the first shaft (3) of which with the camshaft (5) , the second shaft (4) of which is connected to the crankshaft via a camshaft drive wheel (7) and the third shaft of which, as an adjusting shaft (6), is connected to a permanent magnet rotor (8) of a BLDC motor (2), the BLDC motor (2) has a housing-fixed stator (9) with preferably three phases and an electronic commutation which is controlled by commutation signals which are used at the same time to determine the angular position of the camshaft (5) and together with the signals from the crankshaft trigger wheel to calculate the angle of rotation ΔΦ between the camshaft (5) and the crankshaft.

2. Device according to claim 1, characterized in that the crankshaft trigger wheel is designed as a ring gear or resolver and that the commutation signals can be generated by Hall or reluctance sensors, by optical, inductive or capacitive sensors or sensorless by self-induction in the phases of the stator (9) ,

3. Apparatus according to claim 2, characterized in that the sensors in components of the BLDC motor (2) can be installed, which rotate at rotor speed, such as. B. bearing or sealing rings.

4. The device according to claim 3, characterized in that a RAM or an EPROM are provided in a control unit or an active, storable Hall sensor, which counters and thus the position of the camshaft (5) at standstill or when starting the internal combustion engine save or make recognizable.

5. A method for determining the angle of rotation ΔΦ between a camshaft (5) and the crankshaft of an internal combustion engine, in particular using the features of the independent device claim 1, characterized in that the angle of rotation ΔΦ is calculated by additive and multiplicative combinations of the commutation and trigger wheel signals becomes.

6. The method according to claim 5, characterized in that a counter-based calculation of the angle of rotation ΔΦ is based on the following relationship using the commutation signals from Hall sensors: f A -nZählTriggαniarkc 1 nZahll-alls. ₈ i.alc 360 ΔΦ = AnZ t tRefercnz-iwkc "" x- X total number τrιgs _™ rt- 2 A count magn tpole

7. The method according to claim 6, characterized in that the trigger mark signals determined after passing through a reference mark are deleted after reaching the next reference mark.

8. The method according to claim 7, characterized in that a change in the direction of rotation of the BLDC motor (2) is determined by evaluating the change occurring in the commutation signals, for which purpose these are differentiated.

9. The method according to claim 8, characterized in that the differential of the commutation signals of one of the three Hall sensors with the status (High / Low) of the differentials of the other two commutation signals is combined.

10. The method according to claim 5, characterized in that a time-based calculation of the angle of rotation ΔΦ is based on the following relationship: _A. ₊ . r ( ^{nκw ■ •} 2 - nvw),,. ΔΦ = ^ x dt, where ^J in _K w = crankshaft speed; n = speed of the BLDC motor (2) and i = gear ratio between the adjusting shaft (6) and the camshaft (5) with the drive wheel (7) stationary.

11. The method according to claim 9, characterized in that the counter and the time-based determination of the twist angle ΔΦ can be combined with one another.

12. The method according to claim 10, characterized in that the camshaft (5) moves to a reference position, for example a base position with a mechanical stop, in order to zero the counters when the counter and time-based determination of the angle of rotation .DELTA..phi.

13. The method according to claim 10, characterized in that with an integral ratio of the crankshaft and camshaft signals, the phase position of the camshaft to the crankshaft is determined by evaluating the difference of these signals in a position controller, which preferably works with the camshaft or crankshaft speed applied

14. The method according to claim 11, characterized in that the camshaft (5) after switching off the ignition and when the internal combustion engine runs out can be adjusted in any desired position by a trailing BLDC motor (2) or by a control unit run-on.