DE112014003646B4 - Method for determining a position of a linearly moving actuator transmission in an actuator system, in particular a clutch actuation system of a motor vehicle and an actuator system - Google Patents

Abstract

Method for determining a position of a linearly moving actuator transmission, in particular a clutch actuation system of a motor vehicle, in which the actuator transmission (12, 19) is driven by an electric motor (14) and a position signal of a rotor (17) of the electric motor (14) is driven by a sensor (20) is removed, with a sensor designed as an absolute angle sensor (20) measuring a current angle (φ) as a position signal of the rotor (17), which angle (φ0) of one revolution of the rotor (17) is determined during an initialization process as a function of an initial angle (φ0) ) is assigned, from which the position of the actuator gear (12, 19) is determined, characterized in that the currently measured angle (φ) is compared with a critical angle (φG), if the currently measured angle (φ) is below the critical angle (φG), which is smaller than the initial angle (φ0), the currently measured angle (φ) to the next larger rotation of the rotor rs (17) belongs, while, if the currently measured angle (φ) is above the critical angle (φG), which is greater than the initial angle (φ0), the currently measured angle (φ) to the next smaller rotation of the rotor (17) belongs.

Description

The invention relates to a method with the features according to the preamble of claim 1 and an actuator system according to the preamble of claim 5 for carrying out the method.

DE 10 2006 056 515 A1 discloses a method for controlling a clutch.

DE 10 2010 018 620 A1 discloses a method for classifying a coupling unit.

DE 10 2011 105 502 A1 discloses a method for adjusting a phase offset between a rotor position sensor and the rotor position of an electrically commutated motor.

DE 10 2010 048 493 A1 discloses a method for slip control of a friction clutch and a clutch actuator therefor.

EP 1 898 122 A2 discloses an actuating device for linearly adjusting an actuator.

In modern motor vehicles, especially passenger cars, automated clutches are increasingly used, as in the DE 10 2011 014 936 A1 are described. The use of such clutches has the advantage of improved driving comfort and means that it is possible to drive more frequently in gears with a long gear ratio. The clutches used here are used in hydraulic clutch systems in which an electrohydraulic actuator, which is driven by an electrically commutated electric motor, is connected to the clutch via a hydraulic line. For correct commutation, the electric motor has a sensor which detects the position of the rotor of the electric motor during operation of the actuator.

It is known to use different actual position detection systems for the path control of electromotive actuators in, for example, an electrohydraulic clutch actuation system. These can be divided into the group of absolute displacement sensors and the group of incremental displacement sensors. With the help of an incremental displacement sensor, only relative movements of the actuator are recorded. A correct position of the actuator can only be determined here after referencing, i.e. a comparison at a position determined by an independent process. The simplest variant of such a position referencing is the approach of a mechanical end stop by the actuator.

Such position referencing can be carried out in different ways. In actuator systems with high mechanical actuator efficiency, by approaching the stop with a defined motor current or a defined motor voltage, a torque equilibrium position can be found in which, apart from the friction in the actuator system, an equilibrium is established between the motor torque and the torque from the stop force of the actuator.

If the actuator efficiency is poor, the uncertainty of the position found is greater due to the friction. For referencing, the stop must be approached again with a defined force, torque, motor current or motor voltage but at a lower speed, i.e. with lower kinetic energy, so that the actuator only moves slightly into the friction area. Alternatively, the actuator speed when moving against the stop can be evaluated with constant voltage in order to recognize the load structure of the actuator and to carry out referencing. The accuracy of the referencing increases as the stiffness of the stop increases.

A stop force range (scatter of the mechanical parameters and the motor parameters) can be set via the actuator motor voltage. Together with the friction in the system, this results in a path area on which the actuator can come to a standstill. The stiffer the stop, the shorter the travel range.

The stop and the mechanical system of the actuator must absorb the kinetic energy of the moving actuator without the actuator system being destroyed. Given a given kinetic energy E _K , which essentially results from the rotational energy of the rotor of the electric motor at maximum speed, an assumed efficiency of the actuator gear and an assumed linear stop stiffness c, a sensing force F at the stop results without assuming any additional force from the electric motor . $$\mathrm{F.}=\sqrt{2c\eta {\mathrm{E.}}_K}$$

As the referencing accuracy increases, there is an increasing risk of mechanical overloading of the actuator. This is done using the 11 and 12 clarifies where the 11 represents a soft stop in which the actuator is moved against the stop with a lower kinetic energy, and 12 a stiff stop shows where the actuator is operated with a higher kinetic energy. The stop forces and moments are shown as negative here, since the clutch actuation forces are positive by convention. In both 11 , 12 corresponds to the horizontal position the load torque for moving the actuator downwards. In the area A, where the straight line I bends, the force of the actuator acts on the stop. The dashed line II, which is also shown bent to the horizontal curve I, shows the uncertainty of the tactile dynamics. A comparison of the 11 and 12 shows that the reference window Rw for a soft stop is larger than the reference window Rst for a stiff stop. The area G running parallel to the motor angle corresponds to the accuracy of the sensing torque of the sensor.

The invention is therefore based on the object of specifying a method and a device for determining a position of a linearly moving actuator gear, in which referencing can take place with a soft stop.

This object is achieved by a method with the features according to claim 1 and by an actuator system with the features according to claim 5.

According to the invention, the object is achieved in that a sensor designed as an absolute angle sensor measures a current angle as a position signal of the rotor, which is assigned to one rotation of the rotor as a function of an initial angle determined during an initialization process, from which the position of the actuator gear is determined. The method has the advantage that displacement sensors are completely dispensed with and the distance covered by the actuator gear can be determined from the currently measured angle. It can be reliably determined in which rotation of the rotor of the electric motor the angle measured by the absolute angle sensor lies. This is particularly possible because absolute angle sensors use one or only a few revolutions per motor shaft revolution. In this context, rotation is to be understood as covering a complete number of pole pairs N, which is formed on a rotary angle magnet arranged on the rotor of the electric motor. The sensor signal thus passes through its full range of values N times per revolution. For a positive-locking actuator gear with a fixed, unchangeable relationship between the angle of the electric motor and the position of the actuator gear, the requirement for referencing accuracy is reduced.

According to the invention, the currently measured angle is compared with a limit angle, with, if the currently measured angle is below the limit angle, which is smaller than the initial angle, the currently measured angle belongs to the next larger revolution of the electric motor, while if the currently measured angle is above of the critical angle, which is greater than the initial angle, the currently measured angle belongs to the next smaller revolution of the electric motor. It takes into account whether the initial angle is closer to the transition points, i.e. the overflow or underflow of the sensor signal. The limit for the assignment change to the revolutions is represented by the sensor signal with an angular distance of 180 ° to the initial angle. This means that the measured angle can be clearly defined in relation to the distance covered by the actuator gear.

In one embodiment, a reference window for a referencing stop of the actuator transmission is assigned to the initial angle during the initialization process. The initialization process represents a process which is carried out independently of the normal operating process of the actuator system, so that error influences from the environment of the actuator system or aging of the actuator system within the motor vehicle are prevented.

In one variant, the initialization process is carried out at the end of the production line for the actuator system. The initial angle found during the initialization process and the reference window are stored and can be used during operation of the actuator system in the motor vehicle.

During the use of the actuator system in the motor vehicle, the actuator gearbox moves against the referencing stop in a referencing process, the referencing stop being assigned the currently measured angle of the absolute angle sensor and, at the same time, the rotation of the electric motor. This ensures that the angle determined during operation of the actuator system in the motor vehicle also corresponds to the path actually covered by the actuator transmission.

Furthermore, the reference window determined during the initialization process is smaller than an operating reference window while the actuator system is in use in the motor vehicle. Since the referencing and initialization of the actuator gear takes place under defined conditions at the end of the line (temperature, wear and the like), there are smaller scatter in the motor parameters and in the friction of the mechanical system. In contrast, during operation in the motor vehicle, changing conditions can be assumed, so that there are greater fluctuations in the temperature, the state of wear or the aging of the actuator system, so that the operating reference window is selected larger than the reference window during the initialization process. However, it can be assumed that the reference window is always within of the operating reference window in order to enable a precise evaluation of the signal from the absolute angle sensor.

A further development of the invention relates to an actuator system for carrying out the method, in particular a clutch actuation system of a motor vehicle, with an actuator transmission which is driven by an electric motor and which converts a rotary movement of the electric motor into a linear movement of a clutch, a sensor detecting a position of the electric motor . In an actuator system in which the travel of the actuator gear can be referenced with a soft stop, the sensor is designed as an absolute angle sensor and the actuator gear is designed with a true ratio. In the following, true to translation should be understood to mean a relationship that can be reproduced over the service life of the actuator system between the angle of the electric motor and the travel of the actuator transmission and thus the clutch. Such a configuration has the advantage that displacement sensors are completely dispensed with and the route covered by the actuator transmission can be determined from the currently measured angle.

Advantageously, the absolute angle sensor is arranged opposite a rotation angle magnet, which is arranged on a rotor of the electric motor and is preferably designed as a dipole, with a referencing stop being arranged on a side of the actuator gear opposite the electric motor or on the side of the actuator gear facing the electric motor, the absolute angle sensor with an evaluation device is connected, which determines the position of the referencing stop from an angle measured by the absolute angle sensor. The use of such a cost-effective rotary angle magnet simplifies the assignment of the measured angle to the rotation of the electric motor.

In one embodiment, the referencing stop is preceded by a spring-like element with a non-linear force characteristic for absorbing the kinetic forces of the actuator. As a result, the forces transmitted from the actuator gear to the referencing stop are weakened in that the kinetic energy of the actuator gear is reduced before it reaches the referencing stop. It is advantageous to use a suitable non-linear force characteristic of the spring-like element, so that the stop is sufficiently rigid for referencing with the tactile force, but still larger kinetic energies can be absorbed without mechanically overloading the actuators. A suitable disc spring can be used here.

The invention allows numerous embodiments. Several of these will be explained in more detail with reference to the figures shown in the drawing.

• 1: eine vereinfachte Darstellung eines Kupplungsbetätigungssystems zur Betätigung einer automatisierten Reibungskupplung,
• 2: Prinzipdarstellung eines ersten Ausführungsbeispiels eines Spindelaktors gemäß 1,
• 3: ein zweites Ausführungsbeispiel eines Spindelaktors gemäß 1,
• 4: ein drittes Ausführungsbeispiel eines Spindelaktors gemäß 1,
• 5: ein viertes Ausführungsbeispiel eines Spindelaktors gemäß 1,
• 6: ein Ausführungsbeispiel eines Anschlag-Lastkennfelds des Spindelaktors mit Tellerfederanschlag ,
• 7: ein Initialwinkel in der Mitte einer Umdrehung des Spindelaktorantriebes,
• 8: ein Initialwinkel nahe der oberen Winkelgrenze des Spindelaktorantriebes,
• 9: ein Initialwinkel nahe der unteren Winkelgrenze des Spindelaktorantriebes,
• 10: Referenzierungsverhältnisse zwischen einem Referenzfenster des Initialisierungsprozesses und dessen Lage im Betriebreferenzfenster,
• 11: Darstellung des Lastmomentes am Elektromotor über dem Motorwinkel bei einem weichen Anschlag des Aktors nach dem Stand der Technik,
• 12: Darstellung des Lastmomentes am Elektromotor über dem Motorwinkel bei einem steifen Anschlag des Aktors nach dem Stand der Technik.

Show it:

• 1 : a simplified representation of a clutch actuation system for actuating an automated friction clutch,
• 2 : Schematic representation of a first embodiment of a spindle actuator according to 1 ,
• 3 : a second embodiment of a spindle actuator according to 1 ,
• 4th : a third embodiment of a spindle actuator according to 1 ,
• 5 : a fourth embodiment of a spindle actuator according to 1 ,
• 6th : an embodiment of a stop-load map of the spindle actuator with disc spring stop,
• 7th : an initial angle in the middle of one revolution of the spindle actuator drive,
• 8th : an initial angle close to the upper angular limit of the spindle actuator drive,
• 9 : an initial angle close to the lower angular limit of the spindle actuator drive,
• 10 : Referencing relationships between a reference window of the initialization process and its position in the operating reference window,
• 11 : Representation of the load torque on the electric motor over the motor angle with a soft stop of the actuator according to the state of the art,
• 12 : Representation of the load torque on the electric motor over the motor angle with a stiff stop of the actuator according to the state of the art.

The same features are identified by the same reference symbols.

In 1 is an actuator system in the form of a clutch actuation system 1 shown in simplified form for an automated coupling. The clutch actuation system 1 is a friction clutch in a drive train of a motor vehicle 2 assigned and includes a master cylinder 3 via a hydraulic line also known as a pressure line 4th with a slave cylinder 5 connected is. In the slave cylinder 5 is a slave piston 6th movable back and forth, the over one Actuator 7th and with the interposition of a warehouse 8th the friction clutch 2 actuated.

The master cylinder 3 is via a connection opening with an expansion tank 9 connectable. In the master cylinder 3 is a master piston 10 movable. From the master piston 10 goes a piston rod 11 from that in the longitudinal extension of the master cylinder 3 together with the master piston 10 is translationally movable. The piston rod 11 of the master cylinder 3 is via a spindle gear consisting of a threaded spindle 12 and a spindle nut fixedly arranged on the threaded spindle 19th , with an electromotive actuator 13 coupled. The electromotive actuator 13 comprises an electric motor designed as a commutated direct current motor 14th and an evaluation unit 15th . The threaded spindle 12 sets a rotary movement of the electric motor 14th in a longitudinal movement of the piston rod 11 or the master cylinder piston 10 around. The friction clutch 2 is thus by the electric motor 14th who have favourited the lead screw 12 and the master cylinder 3 and the slave cylinder 5 automatically operated.

In 2 a first embodiment of a spindle actuator is shown, which consists of the electric motor 14th . The threaded spindle 12 and a threaded nut 19th consists. The movement of this spindle actuator, in particular that on the threaded spindle 12 seated spindle nut 19th is made by means of an axial absolute angle sensor 20th determines which for referencing the position of the electric motor 14th and the path of the threaded spindle 12 against a stop 23 is driven. The electric motor 14th consists of a rotor 17th and from a stator 18th , with the stator 18th fixed, the one with the gear spindle 12 connected rotor 17th includes. A first end of the lead screw 12 is with a rotating angle magnet 22nd provided, which is preferably designed as a dipole and is connected to the threaded spindle 12 emotional. The axial absolute angle sensor 20th is on a circuit board 21st arranged, which is spaced from the rotary angle magnet 22nd is arranged. On the opposite side of the lead screw 12 becomes the threaded nut 19th as a result of the drive of the threaded spindle 12 through the rotor 17th of the electric motor 14th against the attack 23 driven on which in the direction of the threaded spindle 12 a disc spring 24 is positioned. Instead of the disc spring 24 a differently machined, pretensioned linear spring can also be used.

In 3 a second embodiment of the spindle actuator is shown in which the angle of rotation magnet 22nd between the spindle nut 19th and the rotor 17th of the electric motor 14th is arranged. The absolute angle sensor 20th is in turn on a circuit board 21st attached. In contrast to 2 the absolute angle sensor works 20th as a radial angle sensor and is spaced from the end face of the rotary angle magnet 22nd arranged.

4th shows a third embodiment of the spindle actuator, in which the stop 23 with the disc spring 24 between the spindle nut 19th and the rotor 17th of the electric motor 14th is positioned. The disc spring 24 is in the direction of the spindle nut 19th arranged to cushion their stop. It is advantageous to intercept the referencing and stopping force on the shortest possible path. It is therefore advisable to stop 23 between electric motor 14th and spindle nut 19th to place. This means that the spindle and actuator motor bearings remain unloaded by the impact forces. However, it must be ensured here that the frictional torque between the threaded spindle 12 and spindle nut 19th at the stop 23 that can arise when the actuator is clamped, do not become too large.

A fourth embodiment of the spindle actuator is shown 5 . Here is the threaded spindle 12 on a housing 16 attached, the stop 23 through the housing 16 is realized. The disc spring 24 is attached to the housing 26 and takes on the movement of the threaded spindle 12 the threaded nut 19th on. The opposite end of the lead screw 12 is the absolute angle sensor that works as an axial angle sensor 20th assigned to the angle of rotation magnet 22nd is arranged opposite, which on the, the stop 23 (Casing 16 ) opposite end of the threaded spindle 12 is attached. The bearings must 25th the threaded spindle 12 absorb the stop forces.

The stop stiffness of the spindle nut 19th to the stop 23 be set in such a way that a low, required referencing accuracy can be achieved and the level of force when the threaded nut meets 19th on the stop 23 is not exceeded. Especially when using a suitable disc spring 24 with a non-linear force characteristic curve, the maximum force in the collision is also lowered, as it is from 6th emerges. Here the spindle nut moves 19th from right to left, the referencing stop area B _RA beginning when curve I is lowered from the horizontal course in area A. Such a stop on the plate spring 24 allows a force-limited reduction of the kinetic energy (area KA) so that the kinetic energy cannot increase any further and the actuator system is not damaged.

In an ideal system it is assumed that there is always the same reference position between the path of the screw nut 19th to the stop 23 and that from the absolute angle sensor 20th detected angle φ Is found. It happens in the real system but to measurement uncertainties, but with referencing there is always an angular position in the same position range of the thread actuator, ie the same reference window R. , is assigned. When the thread actuator is initialized at the end of the actuator system, a position of the spindle nut is found 19th in a reference window R. saved. This is done by turning the threaded spindle during the initialization process 12 with a specified motor voltage and a resulting force with the threaded nut 19th against the attack 23 is driven. This evaluates where the spindle nut is 19th has stopped and the associated one by the absolute angle sensor 20th certain angles φ as an initial angle φ ₀ saved. This initial angle φ ₀ corresponds to the reference position 0. To ensure that in the reference window R. also always the first position of the revolution of the electric motor 14th is found, the width of the reference window R. less than half a turn of the electric motor 14th set. Only then can the evaluation circuit 15th the position of the correct rotation of the electric motor 14th assign safely.

Liegt der aktuell gemessene Winkel φ oberhalb des Grenzwinkels φ_G , der größer ist als der Initialwinkel φ₀ , so gehört dieser zur nächst kleineren Umdrehung des Elektromotors 14, wie es in 9 dargestellt ist. Ansonsten befinden sich der gemessenen Winkel φ in derselben Umdrehung des Elektromotors 14 wie bei dem Initialisierungsprozess.Is the initial angle found during the initialization process? φ ₀ in the middle of the angle sensor measuring range, ie at 180 °, there is a simple representation of how this is shown 7th can be found. The straight lines running parallel to one another document one revolution of the rotating angle magnet designed as a dipole 22nd from 0 ° to 360 °. The initial angle found during referencing φ ₀ is used directly to determine the position in revolution 0. Is the initial angle φ ₀ closer to the transition points, like these in the 8th and 9 is shown, these must correspond to the position of the initial angle φ ₀ be taken into account. The limit for the assignment change to the revolutions is the sensor signal with an angle of 180 ° from the initial angle φ ₀ . 8th shows the initial angle φ ₀ near the upper angular limit φ _min . Is the currently measured angle φ caused by the stop during a referencing process 23 the threaded spindle 12 was measured below a critical angle φ _G that is smaller than the initial angle φ ₀ is, then the currently measured angle belongs φ to the next higher revolution of the electric motor 14th . For the critical angle φ _G it is assumed: $${\mathrm{\phi }}_{\text{G}}={\mathrm{\phi }}_0\pm 180°$$

Is the currently measured angle φ above the critical angle φ _G that is greater than the initial angle φ ₀ , it belongs to the next smaller revolution of the electric motor 14th as it is in 9 is shown. Otherwise the measured angle is located φ in the same revolution of the electric motor 14th as with the initialization process.

During the initialization process, it is assumed that defined conditions, such as a constant temperature, a low level of wear and the like, are present. In the later operation of the actuator system in the motor vehicle, however, these defined conditions will change. It is therefore assumed that the reference window R. of the initialization process is smaller than the operational reference window R _B in later operation. Both widths of the reference window R. and the operational reference window R _B are estimated, but can also be determined experimentally. The reference window is also located R. not centered in the operational reference window R _B . This offset is also known. This then results in the angle limits and the relative position of the critical angle φ _G to the initial angle φ ₀ , as in 10 shown. If these boundary conditions are known with sufficient accuracy, the reference window R. also be slightly larger than half a turn of 180 ° of the electric motor 14th .

The solution described comprises, in a generalization, an actuator with a slip-free, form-fitting actuator gearbox between the actuator motor with the motor angle sensor and the actuator position to be determined. A high-resolution absolute angle sensor is used to record the actuator motor angle and a defined, soft position stop at the actuator position to be determined on the spindle nut 19th for actuating a master piston 10 set for referencing the distance measurement, so that there is a minimum resolution of approx. 0.5 revolutions of the electric motor 14th on the absolute angle sensor 20th results. The advantage of the invention consists in the utilization of the fixed relationship between actuator travel and motor angle when using an absolute angle sensor on the actuator motor in order to significantly increase the referencing accuracy in the form of limiting the impact force despite the mechanical stop that is not too hard.

List of reference symbols

1

Clutch actuation system

2

Friction clutch

3

Master cylinder

4th

Hydraulic line

5

Slave cylinder

6th

Slave piston

7th

Actuator

8th

camp

9

surge tank

10

Master piston

11

Piston rod

12

Threaded spindle

13

Electromotive actuator

14th

Electric motor

15th

Evaluation unit

16

casing

17th

rotor

18th

stator

19th

Spindle nut

20th

Absolute angle sensor

21st

circuit board

22nd

Rotation angle magnet

23

attack

24

Disc spring

25th

camp

R.

Reference window of the initialization process

R _B

Operation reference window

R _w

Reference window with a soft stop

R _St

Reference window with rigid stop

φ

measured angle

φ ₀

Initial angle

φ _G

Critical angle

φ _Max

maximum limit angle

φ _min

minimum critical angle

Claims (7)

Method for determining a position of a linearly moving actuator transmission, in particular a clutch actuation system of a motor vehicle, in which the actuator transmission (12, 19) is driven by an electric motor (14) and a position signal of a rotor (17) of the electric motor (14) is driven by a sensor (20) is removed, with a sensor designed as an absolute angle sensor (20) measuring a current angle (φ) as a position signal of the rotor (17), which angle (φ ₀ ) of one revolution of the rotor (φ 0) determined during an initialization process is 17) is assigned, from which the position of the actuator gear (12, 19) is determined, characterized in that the currently measured angle (φ) is compared with a critical angle (φ _G ), if the currently measured angle (φ) is below of the critical angle (φ _G ), which is smaller than the initial _{angle (φ 0} ), the currently measured angle (φ) to the next larger revolution of the rotor (17) belongs, while if the currently measured angle (φ) is above the critical angle (φ _G ), which is greater than the initial _{angle (φ 0} ), the currently measured angle (φ) to the next smaller rotation of the rotor (17) heard. Procedure according to Claim 1 , characterized in that during the initialization process the initial angle (φ ₀ ) is assigned a reference window (R) for a referencing stop (23) of the actuator gear (12, 19). Procedure according to Claim 2 , characterized in that the initialization process is carried out at the end of the production line for the actuator system (1). Method according to one of the preceding Claims 2 or 3 , characterized in that the reference window (R) determined during the initialization process is smaller than an operating reference _{window (R B} ) while the actuator system (1) is in use in the motor vehicle. Actuator system, in particular a clutch actuation system of a motor vehicle, with an actuator gear (12, 19) which is driven by an electric motor (14) and which converts a rotary movement of the electric motor (14) into a linear movement of a clutch, with a sensor recording a position of the electric motor (14), wherein the sensor is designed as an absolute angle sensor (20) and the actuator gear (12, 19) is designed to be true to the ratio, characterized in that a method according to one of the Claims 1 to 4th is carried out. Actuator system according to Claim 5 , characterized in that the absolute angle sensor (20) is arranged opposite a rotation angle magnet (22) arranged on a rotor (17) of the electric motor (14), preferably designed as a dipole, the referencing stop (23) on one of the electric motor (14) opposite side of the actuator gear (12, 19) or is positioned on the side of the actuator gear (12, 19) facing the electric motor (14), the absolute angle sensor (20) being connected to an evaluation device (15) which consists of a, The angle (φ) measured by the absolute angle sensor (20) determines the position of the referencing stop (23). Actuator system according to Claim 5 or 6th , characterized in that the referencing stop (23) is preceded by a spring-like element (24) with a non-linear force characteristic for absorbing the kinetic forces of the actuator gear (12, 19).

Images