Method for positioning a rotor shaft of an electric motor, computer program, computer program product, system, and vehicle

Abstract

The invention relates to a method for positioning a rotor shaft (RW) of an electric motor, having the steps of: - determining the initial position of the rotor shaft (RW) from a plurality of definable rotational angle positions of the rotor shaft (RW) in which the rotor shaft (RW) can be locked or unlocked without restriction by means of a form-fitting element (FE) of a locking actuator (SA), wherein in order to determine said initial position, the rotor shaft (RW) is divided into individual circular segment sections over the circumference of the rotor shaft such that one form-fitting element section is paired with each of the circular segment sections, said form-fitting element section being capable of being joined to a complementarily shaped form-fitting element section of the locking actuator (SA), - positioning the rotor shaft (RW) in one of the rotational angle positions, the absolute rotational angle position of the rotor shaft (RW) being detected by means of a rotor (shaft) position sensor, and - locking or unlocking the rotor shaft (RW) in said rotational angle position in that the form-fitting element (FE) is moved into or out of the rotor shaft (RW) in a stroke movement. The invention additionally relates to computer program, to a computer program product, to a system, and to a vehicle.

Description

[0001] Description

[0002] Method for positioning a rotor shaft of an electric motor, computer program, computer program product, system and vehicle

[0003] The invention relates to a method for positioning a rotor shaft of an electric motor, in particular for driving a vehicle.

[0004] The invention also relates to a computer program and a computer program product, each of which depicts this method, to a system having a locking actuator and a control unit connected to the locking actuator, wherein the control unit has such a computer program or computer program product, and to a vehicle having such a computer program or computer program product.

[0005] Parking locks are known in which an electrically actuated lever with a ratchet tooth interacts with a gear of a drive train to block or lock the drive train. For example, see DE 102017 102 804 A1, which describes such a parking lock with a ratchet mechanism.

[0006] Parking locks are also known whose locking mechanism or locking element can be adjusted or moved linearly along a path of movement. For example, DE 10 2019 110 384 A1 describes such a parking lock with a locking pin.

[0007] The object of the present invention is to improve both the locking and unlocking of such a parking lock.

[0008] This object is achieved by a method proposed and protected according to claim 1. A method for positioning a rotor shaft of an electric motor, in particular for driving a vehicle, is proposed, comprising the method steps:

[0009] - Determining an initial position of the rotor shaft from a plurality of definable rotational angle positions of the rotor shaft, in which the rotor shaft can be locked or unlocked without constraint by means of a form-locking element of a locking actuator, wherein, to determine this initial position, the rotor shaft is subdivided over its circumference into individual circular segment sections in such a way that each of these circular segment sections is assigned a form-locking element section which can be joined to a complementarily shaped form-locking element section of the locking actuator,

[0010] - Positioning the rotor shaft in one of these rotational angle positions, whereby an absolute rotational angle position of the rotor shaft is detected by means of a rotor (shaft) position sensor, and

[0011] - Locking or unlocking the rotor shaft in this rotational angle position by moving the form-locking element in a lifting movement into or out of the rotor shaft.

[0012] Using a so-called rotor (shaft) position sensor, the position or orientation of an electric motor's rotor, and thus the position or orientation of the rotor shaft on which the rotor is mounted, can be precisely determined relative to the three phases or the poles of a stator of the electric motor. The rotor (shaft) position sensor thus enables efficient commutation of the electric motor on the one hand, and provides an absolute angular position of the rotor shaft on the other.

[0013] The rotor (shaft) position sensor can be implemented in the form of an inductively acting signal transmitter or in the form of a Hall sensor, the functioning of which is sufficiently known to those skilled in the art. The rotor (shaft) position sensor can be provided on the electric motor side or the vehicle drive side, i.e., on a vehicle's traction drive in the form of an electric motor, or on the locking actuator side, i.e., on the locking actuator.

[0014] An initial position of the rotor shaft is understood to be an ideal rotational angle position or ideal position of the rotor shaft relative to the positive locking element of the locking actuator, namely from a plurality of definable, ideal rotational angle positions or ideal positions of the rotor shaft, in which the rotor shaft is positioned or aligned relative to the positive locking element in such a way that the rotor shaft can be locked or unlocked without constraint by means of the positive locking element of the locking actuator.

[0015] Constraint-free means that the two interacting form-locking element sections do not come into contact with their associated flanks in the circumferential direction of the rotor shaft or the locking actuator, or that they mesh with each other without contact, or that they are in contact with each other without contact.

[0016] Starting from this – once determined – initial position, the rotor shaft can be rotated or moved to the respective ideal positions according to the aforementioned, definable division of the rotor shaft across its circumference into the aforementioned circular segment sections, and taking into account its current, precisely recorded angular position. These so-called ideal positions represent support points that are stored in the software or computer program of a control unit for controlling or rotating the rotor shaft.

[0017] The proposed method therefore enables a constraint-free locking or unlocking of the rotor shaft by the said positive-locking element of the locking actuator. This is because the two interacting positive-locking element sections are positioned or aligned with each other for the purpose of locking or unlocking the rotor shaft such that no contact is made with respect to their flanks in the circumferential direction of the rotor shaft or the locking actuator. A positive connection between the two positive-locking element sections is thus established without contact with respect to these flanks, or it is released without contact with respect to these flanks. Thus, from the perspective of the locking actuator, locking or unlocking can be performed with optimized force, i.e., with minimal force.

[0018] This force-optimized actuation of the locking actuator, in turn, allows the locking actuator to be as small and compact as possible while remaining sufficiently robust, meaning it can be designed cost-effectively and with minimal weight. This also simplifies the assembly effort for such a locking actuator.

[0019] It is proposed that ideal rotational angle positions be used in which the two interacting positive-locking element sections do not enclose any relative angle to each other. This means that the two positive-locking element sections are located or arranged centrally relative to each other in the circumferential direction of the rotor shaft or the locking actuator.

[0020] Alternatively, rotational angle positions in the sense of ideal positions can also be used, in which the two interacting form-locking element sections enclose a relative angle to one another or to one another, so that they form an off-center arrangement in the circumferential direction of the rotor shaft or the locking actuator, provided that no contact is established with respect to the said flanks of the form-locking element sections in the circumferential direction of the rotor shaft or the locking actuator. In this case, a mechanical play between the two form-locking element sections in the circumferential direction of the rotor shaft or the locking actuator would be provided accordingly. Such mechanical play enables - depending on the design - a multitude of possible positions of the two interacting form-locking element sections relative to one another, in which the said contact between the said flanks does not occur.It is proposed to use a uniform pitch to subdivide the circumference of the rotor shaft. This simplifies the positioning of the rotor shaft, starting from the aforementioned, once determined and fixed initial position.

[0021] One embodiment proposes a locking mechanism in which the positive locking element is moved in an axial stroke movement and longitudinally to the rotor shaft. A rotor shaft with external gearing in a region of one of its ends and a complementarily shaped positive locking element can be used, which is moved in an axial stroke movement and longitudinally to the rotor shaft against and into the rotor shaft.

[0022] The proposed method can be used to secure a vehicle. It is proposed that, after the positive locking element has been moved into the rotor shaft without constraint, the rotor shaft is struck against the positive locking element in a defined clockwise or counterclockwise direction to clamp the rotor shaft against the positive locking element. The rotor shaft can be struck against the positive locking element until a definable electromotive shutdown torque of the electric motor is reached, at which point the rotation of the rotor shaft is interrupted.

[0023] The switching-off torque of the electric motor corresponds to a monitorable current consumption of the electric motor, so that when a definable reference value for the current consumption is reached, the electric motor is switched off or the rotation of the rotor shaft is interrupted.

[0024] This deliberately induced tension creates effective tamper protection, preventing or at least significantly complicating unlocking of the locking actuator by third parties or unauthorized persons. If an attempt is made to manipulate the locking actuator while the locking mechanism is in its tensioned state, for example by applying current to the actuator, the force generated by the actuator is insufficient for the unlocking process. The proposed method can also be used to relieve tension on a rotor shaft that has been struck and tensioned against the form-locking element due to load. The rotor shaft is positioned in the rotational angular position in which it was previously locked without constraint in order to relieve tension on the rotor shaft. The form-locking element is then moved out of the rotor shaft without constraint.

[0025] Such a load-related, strained rotor shaft condition occurs, for example, when a vehicle is parked at an angle, for example, due to a curb on which it rests with only one tire. When the locking actuator is locked, the drivetrain is subjected to strain because the vehicle rests against the locking actuator. In such a vehicle condition, a greater unlocking force is required from the locking actuator to unlock the locking actuator than when the vehicle is parked level.

[0026] Consider, for example, a parking situation where a vehicle is parked on a road with an uphill or downhill gradient. In such a situation, the vehicle also leans against the parking lock due to a downward force acting on the vehicle, which in turn tends to move the vehicle.

[0027] Furthermore, a computer program for carrying out the method described above is proposed, as well as a computer program product comprising program code means stored on a computer-readable data carrier for carrying out the method described above when the program code means are executed on a computer.

[0028] Furthermore, a system with a locking actuator and a control unit connected to the locking actuator is proposed, wherein the control unit has a computer program or a computer program product of the type described above, as well as a vehicle with a computer program or a computer program product of the type described above.

[0029] A vehicle is defined as any type of vehicle or motor vehicle powered by an electric motor, but in particular includes passenger cars and / or commercial vehicles in the form of electric or hybrid vehicles. These can be semi-autonomous or fully autonomous vehicles.

[0030] They show, partly schematically:

[0031] Fig. 1 shows an arrangement of a locking actuator and a lockable rotor shaft of an electric motor,

[0032] Fig. 2 is a systemic representation of an inverter with a control unit and the locking actuator shown in Fig. 1 with a control unit,

[0033] Fig. 3 shows a locking process of the locking mechanism shown in Fig. 1 and

[0034] Fig. 4 shows an unlocking process of the locking mechanism shown in Fig. 1.

[0035] The locking mechanism according to Fig. 1 illustrates two form-locking elements that are complementary to one another and rotatable relative to one another, namely a first form-locking element FE of a locking actuator SA and a second form-locking element in the form of a lockable rotor shaft RW of an electric motor (not shown) for driving a vehicle. The locking actuator SA is attached to a housing (not shown) of the electric motor of an electric motor drive unit, which as such can comprise a transmission, and can therefore be supported on this housing. Depending on the state of the locking mechanism, these two form-locking elements FE, RW are arranged coaxially to one another (unlocked state) or concentrically in sections (locked state).

[0036] In this case, an internal toothing IV of the form-locking element FE interacts with an external toothing AV of the rotor shaft RW, which is formed as such in a region of one end of the rotor shaft RW, in that the form-locking element FE is electrically actuated in an axial stroke movement and longitudinally to the rotor shaft RW and is joined to the rotor shaft end in sections.

[0037] The vehicle in question, which includes this locking mechanism, has an electric motor drive unit with an electric motor in the form of a permanent magnet or separately excited synchronous machine for driving the vehicle. The electric motor can optionally be combined with a reduction gear. It also includes a high-voltage battery, and an inverter, which is included in the vehicle's power electronics and establishes the connection between the electric motor and the high-voltage battery. The power electronics can optionally include an integrated voltage converter, which supplies a low-voltage electrical system of the vehicle from the vehicle's high-voltage electrical system.

[0038] An inverter control unit controls, regulates, and monitors the electric motor, ensuring torque and speed control of the vehicle's drivetrain as required. The inverter also converts the DC voltage of the high-voltage battery into the AC voltage required by the electric motor.

[0039] The power electronics or the inverter included in the power electronics not only supplies the electric motor with power, but also the high-voltage battery - namely when the electric motor is operating as a generator and feeding power into the high-voltage battery. During this process, known as recuperation, it converts the alternating current generated by the electric motor into direct current and uses this to charge the high-voltage battery. Fig. 2 illustrates a systemic connection between the inverter in question or an inverter-specific control unit SEinv and the locking actuator or a locking actuator-specific control unit SESA. The control unit SEinv outputs a control command SB to the control unit SESA depending on input parameters FP of the vehicle (FP = vehicle parameter), whereupon the locking actuator SA locks or unlocks the rotor shaft RW. The control unit SESA generates an actuator state AZ and a locking or unlocking state.Lock status VZ displayed or output.

[0040] Fig. 3 illustrates a wound arrangement of the internal toothing IV of the positive locking element FE and the external toothing AV of the rotor shaft RW relative to each other, specifically relative to a circumferential direction and a longitudinal direction of the two positive locking elements FE, RW. The internal toothing IV is stationary relative to the circumferential direction of the two positive locking elements FE, RW, and the external toothing AV is rotatable relative to the internal toothing IV.

[0041] Both the form-locking element FE and the rotor shaft RW are divided into uniform circular segment sections according to a definable common division over the respective assigned circumference (circular segment section = 3607n; n = number of teeth), which thus all have the same angular extension.

[0042] In the wound representation according to Fig. 3, this angular extent of such a circular segment section is illustrated as the segment length SL. And, relative to a radius from the center of the form-locking element FE or the center of the rotor shaft RW, this angular extent corresponds to a pitch-related arcuate distance between the centers of two adjacent teeth of the internal toothing IV or the centers of two adjacent tooth gaps of the external toothing AV.

[0043] This segment length SL according to Fig. 3 – expressed in degrees (angle) – describes a step size from one ideal alignment to the next ideal alignment of the two form-locking elements FE, RW relative to one another, whereby in these ideal alignments, the respectively assigned segment lengths SL do not exhibit or include any angular offset relative to one another. This means that these respectively assigned segment lengths SL coincide exactly relative to one another and thus represent no displacement or deviation from one another in the circumferential direction of the two form-locking elements FE, RW.

[0044] Such an ideal alignment of the two form-locking elements FE, RW to one another is illustrated by the uppermost arrangement of the internal toothing IV and the external toothing AV shown in Fig. 3. In this arrangement, the two form-locking elements FE, RW are not joined to one another. The locking mechanism formed by the two form-locking elements FE, RW is therefore unlocked. One of these ideal alignments in a direction of rotation of the rotor shaft RW is considered to be an initial position or

[0045] -position to be determined in which the two form-locking elements FE, RW can be joined together with respect to the respective assigned tooth flanks without contact and thus without constraint and consequently with optimized force from the point of view of the locking actuator SA.

[0046] Once this initial position has been determined, the rotor shaft RW can be rotated into the respective ideal orientations or corresponding rotational angle positions according to the specified pitch, i.e., the number of circular segment sections defined by the number of teeth (illustrated by the penultimate arrangement in Fig. 3). In this process, the absolute rotational angle position of the rotor shaft RW is precisely recorded using a rotor (shaft) position sensor.

[0047] In this way, the circumferences of the two form-locking elements FE, RW can be divided into, for example, n = 32 circular segment sections (because each has 32 teeth), resulting in uniform circular segment sections of 360732 = 11.25°. The said ideal alignments or the corresponding rotational angle positions of the rotor shaft RW thus represent support points that are stored as such in the control unit SEinv and can be approached. The second and third arrangements of the internal toothing IV and the external toothing AV shown in Fig. 3 each illustrate a deviation Abw. 01, Abw. 02 between the assigned segment lengths SL, whereby these deviations Abw. 01, Abw. 02 do not permit a form-locking of the locking mechanism.

[0048] In a parking situation in which the vehicle is to be brought to a standstill and locked, the rotor shaft RW can be rotated in a first or in a second direction of rotation opposite thereto, or clockwise or counterclockwise, until it reaches one of the said ideal orientations.

[0049] The rotor shaft RW can be rotated – following the shortest path – to the nearest ideal orientation or to the next support point, i.e., to the ideal orientation that encloses the smallest angle with the currently recorded absolute rotational angle position of the rotor shaft RW or forms the smallest angular difference, provided the ambient conditions permit. The rotor shaft RW is thus rotated by one of these recorded angular differences to the corresponding support point.

[0050] In the penultimate arrangement shown in Fig. 3, which illustrates such an ideal alignment of the rotor shaft RW to the positive locking element FE, the control unit SEinv of the inverter outputs the control command SB to lock the rotor shaft RW to the control unit SEA of the locking actuator SA, whereupon the positive locking element FE is eclectically actuated or moved against the rotor shaft RW while the vehicle is stationary (vehicle speed = 0 km / h). The positive locking element FE is moved into the rotor shaft RW without constraint, i.e., without contact with the respective tooth flanks and consequently with optimized force from the perspective of the locking actuator SA.

[0051] The last or lowest arrangement in Fig. 3 illustrates a positive locking of the locking mechanism. The two positive locking elements FE and RW are slightly offset from each other due to play. This means that the associated circular segment sections of the two positive locking elements FE and RW are no longer precisely aligned with each other.

[0052] Fig. 4, on the other hand, illustrates the unlocking or release of the locking mechanism starting from the topmost arrangement shown in Fig. 4, in which a locking or locked state of the locking mechanism is illustrated. This topmost arrangement illustrates a state in which the external toothing AV is abutting against the internal toothing IV. In this arrangement, a deviation Abw. 03 between the respectively assigned segment lengths SL is illustrated.

[0053] This can be caused, on the one hand, by the vehicle being parked on an uneven surface, so that the vehicle leans against the locking actuator SA and thus the housing of the electric motor. This, in turn, causes the rotor shaft RW to be tensioned against the positive locking element FE.

[0054] Such clamping of the rotor shaft RW against the positive locking element FE can also be caused by the rotor shaft RW, after being locked by the positive locking element FE without any constraints, being struck against the positive locking element FE in a defined clockwise or counterclockwise direction in order to clamp the rotor shaft RW against the positive locking element FE in a defined manner. This ensures protection against manipulation by third parties or unauthorized persons, which prevents or at least significantly complicates the unlocking of the locking actuator.

[0055] When the vehicle is started up, the SEA control unit displays a locking status VZ and outputs it to the SEinv control unit. The SEinv control unit outputs a control command SB to unlock the rotor shaft RW to the SEA control unit. The rotor shaft RW is then positioned – with the vehicle stationary (vehicle speed = 0 km / h) and knowing the precisely recorded absolute position or orientation of the rotor shaft RW – into the angular position in which it was previously locked and with which the currently recorded absolute angular position of the rotor shaft RW forms an angle or forms an angular difference in order to release the rotor shaft RW. The rotor shaft RW is then rotated by this angular difference to the last reference point reached.

[0056] The positive locking element FE is then moved out of the rotor shaft RW without any constraints, i.e., without contact with the respective associated tooth flanks and, consequently, with optimized force from the perspective of the locking actuator SA, so that the positive locking of the locking mechanism is released. The vehicle can then be moved.

[0057] The deviation (deviation 03) according to Fig. 4 is not only due to play, i.e., not only due to mechanical play between the positive locking element FE and the rotor shaft RW in the circumferential direction of the locking actuator SA, but also due to the elasticity underlying the locking mechanism, which, as a result of a load acting on the locking mechanism, establishes a corresponding position of the rotor shaft RW relative to the positive locking element FE. This elasticity depends on the design of the two positive locking elements FE and RW.

[0058] Such a deviation (deviation 03), in which the rotor shaft RW is clamped against the positive locking element FE, can also be caused solely by the elasticity underlying the locking mechanism, whereby the deviation (deviation 03) occurs in conjunction with an occurring or occurring load, which as such acts on the locking mechanism. This depends on how the two interacting positive locking elements FE, RW are shaped or formed in certain sections. A gear pair in the form of a Hirthz gear should be mentioned here, which, as such, does not allow any mechanical play.

[0059] The positioning of the rotor shaft RW can be achieved via a so-called speed control or a so-called torque control with a so-called P component and an I component. The aforementioned ideal alignments of the two form-locking elements FE, RW relative to each other, or the corresponding rotational angle positions of the rotor shaft RW, which as such - as described above - represent support points and are stored in the control unit SEinv, can also be learned using a learning or adaptation process, so that manufacturing tolerances between the two form-locking elements FE, RW can be advantageously compensated.

[0060] The previously described control units SEinv, SEA comprise a digital microprocessor unit (CPU) data-connected to a memory system and a bus system, a random access memory (RAM), and a storage device. The CPU is designed to process commands embodied as a program stored in a memory system, to detect input signals from the data bus, and to output output signals to the data bus. The memory system can have various storage media in the form of magnetic, solid-state, and other non-volatile media, on which a corresponding computer program for implementing the method and the advantageous embodiments is stored. The program can be designed in such a way that it embodies or is capable of executing the method aspects described here, so that the CPU can execute the steps of such methods and thus control both the vehicle and the parking lock or locking device.

[0061] Suitable for carrying out the proposed method is a computer program which has program code means for carrying out all the steps of any of the claims or method claims when the program is executed in the CPU.

[0062] The computer program can be easily read into existing control electronics and used to control both the vehicle and the locking actuator—or the parking lock or locking device. A computer program product is provided for this purpose with program code stored on a computer-readable data carrier to carry out the method according to any of the claims when the computer program product is executed in the CPU. The computer program product can also be integrated into the control electronics as a retrofit option.

[0063] Although exemplary embodiments are explained in the foregoing description, it should be noted that numerous modifications are possible. Furthermore, it should be noted that the exemplary embodiments are merely examples and are not intended to limit the scope of protection, applications, or structure in any way. Rather, the foregoing description provides the skilled person with a guide for implementing at least one exemplary embodiment, whereby various modifications, particularly with regard to the function and arrangement of the described components, can be made without departing from the scope of protection as it results from the claims and equivalent combinations of features.

Claims

Patent claims 1 . Method for positioning a rotor shaft (RW) of an electric motor, in particular for driving a vehicle, comprising the method steps: - Determining an initial position of the rotor shaft (RW) from a plurality of definable rotational angle positions of the rotor shaft (RW), in which the rotor shaft (RW) can be locked or unlocked without constraint by means of a form-locking element (FE) of a locking actuator (SA), wherein, to determine this initial position, the rotor shaft (RW) is subdivided over its circumference into individual circular segment sections in such a way that each of these circular segment sections is assigned a form-locking element section which can be joined to a complementarily shaped form-locking element section of the locking actuator (SA), - positioning the rotor shaft (RW) in one of these rotational angle positions, wherein an absolute rotational angle position of the rotor shaft (RW) is detected by means of a rotor (shaft) position sensor, and - Locking or unlocking the rotor shaft (RW) in this rotational angle position by moving the form-locking element (FE) in a lifting movement into or out of the rotor shaft (RW).

2. Method according to claim 1, wherein rotational angle positions are used in which the two form-locking element sections do not enclose a relative angle to one another.

3. Method according to claim 1 or 2, wherein a uniform division is used to subdivide the circumference of the rotor shaft (RW).

4. Method according to one of the preceding claims, wherein the form-locking element (FE) is moved in an axial stroke movement and longitudinally to the rotor shaft (RW).

5. Method according to one of the preceding claims 1 to 4, wherein the rotor shaft (RW), after the form-locking element (FE) has been moved into the rotor shaft (RW) without constraint, is struck in a defined clockwise or counterclockwise direction against the form-locking element (FE) in order to clamp the rotor shaft (RW) against the form-locking element (FE).

6. Method according to one of the preceding claims 1 to 4, wherein a rotor shaft (RW) which is clamped and clamped against the form-locking element (FE) due to load is positioned in the rotational angle position in which it was previously locked without constraint in order to relieve the rotor shaft (RW), and wherein the form-locking element (FE) is subsequently moved out of the rotor shaft (RW) without constraint.

7. Computer program for carrying out a method according to one of the preceding claims 1 to 6.

8. A computer program product comprising program code means stored on a computer-readable data carrier for carrying out the method according to any one of the preceding claims 1 to 6 when the program code means are executed on a computer.

9. System with a locking actuator (SA) and a control unit (SEinv, SESA) for actuating the locking actuator (SA), wherein the control unit (SEinv, SESA) has a computer program product according to claim 8.

10. Vehicle with a computer program product according to claim 9.

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