Method for activating a parking lock of a vehicle, computer program and computer program product for carrying out the method and vehicle

Abstract

Method for actuating a parking lock of an electric motor for driving a vehicle, wherein the parking lock is received by a housing of the electric motor and actuated when a defined reference speed of the vehicle is undershot by a determined vehicle speed, wherein the vehicle speed is determined by means of a rotor position sensor (RPS) integrated into the parking lock, which provides periodic voltage signals for determining the vehicle speed within a control unit of the vehicle.

Description

The invention relates to a method for actuating a parking lock of a vehicle, a computer program and a computer program product for carrying out this method, and a vehicle with such a computer program or computer program product. Parking locks are known in which an electrically actuated lever with a so-called ratchet tooth interacts with a gear of a drive train to block or lock the drive train. For example, German patent application DE 10 2017 102 804 A1 describes such a parking lock with a ratchet mechanism. These parking locks can be activated below a definable, critical vehicle speed limit, the violation of which is monitored by sensors based on a determined vehicle speed. Wheel speed information is used to determine the vehicle speed and is provided to the vehicle's control unit. From publication WO 2021197834 A1, a parking lock or parking lock device is known which is arranged as such on a wheel and includes a sensor device which is configured to determine the rotational speeds of a vehicle's engine and / or the rotational speeds of a vehicle's transmission. In a fault situation in the vehicle's control system, this parking lock enables activation of the parking lock up to a defined maximum vehicle speed. The object of the present invention is to improve the safety of such parking barriers or parking barrier systems. This problem is solved by a method proposed and protected according to claim 1. A method for actuating the parking lock of an electric motor used to propel a vehicle is proposed. The parking lock is engaged by a housing of the electric motor and actuated when a defined reference speed of the vehicle falls below a determined vehicle speed. The vehicle speed is determined by a rotor position sensor integrated into the parking lock, which provides periodic voltage signals for determining the vehicle speed within a control unit of the vehicle. The proposed method is based on the concept of integrating a rotor position sensor into a parking lock. Reference is made here to DE 10 2022 207 258 A1, in which such a concept is disclosed by way of example. In this method, a position sensor arrangement with an inductive signal transmitter and a sensor component, at least partially metallic, that interacts with the signal transmitter is accommodated by a housing of the parking lock. This position sensor arrangement detects the absolute angular position of a rotor connected to a shaft of an electric motor in an electric motor drive unit for propelling a vehicle. Within the scope of the present invention, it is proposed to use such a rotor position sensor not only for efficient electronic commutation of a separately excited or permanent excited synchronous machine of the electric motor drive unit, but also for determining a highly accurate vehicle speed. In a further embodiment, it is proposed that the highly accurate vehicle speed determined in this way be used to validate vehicle speed guidance information derived from other sensor signals, which itself represents primary vehicle speed information for orientation. This vehicle speed guidance information can be determined, for example, from wheel speed sensor signals within a vehicle control unit, such as an ESP control unit (Electronic Stability Program) – also known as an ESC control unit (Electronic Stability Control). This is an electronic driver assistance system designed to counteract vehicle skidding by braking individual wheels. This is also referred to as vehicle dynamics control. This redundancy supports or secures the release of a drivetrain lock by the parking lock (veto option). For example, an inverter control unit can be designed as a central control unit, which can also process signals for the parking lock. In this unit, a first vehicle speed signal is compared with a second vehicle speed signal—that is, the vehicle speed signal determined by the rotor position sensor integrated into the parking lock—to enable a locking request. This compensates for inaccuracies in vehicle speed information determined, for example, based on wheel speed sensor signals. Unintentional activation of the parking lock above the aforementioned reference speed of the vehicle can thus be prevented. In a further version, it is proposed that the vehicle speed determined in this way – which is highly accurate – can itself be used as vehicle speed guidance information, against which plausibility checks can then be performed if necessary. In another version, it is proposed that the vehicle speed determined in this way – with high accuracy – be determined within a control unit integrated into the parking lock. Furthermore, a computer program for carrying out the procedure 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 procedure described above when the program code means are executed on a computer. Furthermore, a vehicle equipped with a computer program or computer program product of the type described above is proposed. The term "vehicle" refers to any type of vehicle or motor vehicle that is electrically powered, but in particular passenger cars and / or commercial vehicles in the form of electric or hybrid vehicles. These may be partially or fully autonomous vehicles. It is also proposed to use a rotor position sensor integrated into a parking lock of an electric motor of an electric motor drive unit for propelling a vehicle to actuate the parking lock, wherein the parking lock is or will be received by a housing of the electric motor, wherein a vehicle speed is determined within a control unit of the vehicle to release a locking request based on periodic voltage signals provided by the rotor position sensor. The invention will now be explained in detail with reference to the figures. Further advantageous embodiments of the invention will become apparent from the dependent claims and the following description of preferred embodiments. For this purpose, a single figure schematically shows: Fig. 1 an electric or hybrid vehicle with a lockable electric motor drive unit. The vehicle 2 illustrated in Fig. 1 comprises an electric motor drive unit 4 with a permanent magnet or separately excited synchronous machine as the electric motor for driving the vehicle, wherein the electric motor may optionally be combined with a reduction gear, a high-voltage battery 8, and an inverter 6, which is part of the vehicle 2's power electronics and establishes the connection between the electric motor of the electric motor drive unit 4 and the high-voltage battery 8. The power electronics may optionally include an integrated voltage converter 10, which supplies the vehicle's low-voltage electrical system from the vehicle's high-voltage electrical system. A control unit of the inverter 6 controls, regulates and monitors the electric motor and ensures a demand-based torque supply and speed control of a drive train of the vehicle 2. In addition, the inverter 6 converts the DC voltage of the high-voltage battery 8 into the AC voltage required by the electric motor. The power electronics, or rather the inverter 6 encompassed by the power electronics, not only supply the electric motor with power, but also the high-voltage battery 8 – namely when the electric motor operates as a generator and feeds current into the high-voltage battery 8. In this process, known as recuperation, it converts the alternating current generated by the electric motor into direct current and thus charges the high-voltage battery 8. The electric motor drive unit 4 incorporates a parking lock – also called a locking device – which in turn integrates a rotor position sensor (RPS). This RPS serves two purposes: firstly, to ensure efficient commutation of the electric motor, and secondly, to provide periodic, sinusoidal voltage signals to a vehicle control unit, such as the control unit of the inverter 6. From these voltage signals, the control unit calculates the absolute angle of the electric motor's rotor, or the precise angular position of the rotor or rotor shaft, as well as its exact rotational speed. By utilizing a fixed or, if applicable, switchable gear ratio between the electric motor's rotor shaft and one of the drive wheels, the control unit can determine the vehicle's speed with high accuracy. The vehicle speed determined in this way can be used to validate vehicle speed guidance information derived from other sensor signals. For example, the vehicle speed determined in this way can be used in the control unit of inverter 6 to validate this vehicle speed guidance information and thus to enable a rotor shaft lock. After such validation and enablement, the control unit of inverter 6 sends a locking command to the parking lock. This redundant determination of the vehicle speed increases the functional reliability of the parking lock. Therefore, the control unit of inverter 6 can, for example, function as a central control unit for the parking lock. Alternatively, the vehicle speed determined in this way can itself be used as vehicle speed guidance information, against which plausibility checks can be performed if necessary. The parking lock itself includes a control unit in which the aforementioned determination of the vehicle speed can be carried out based on the aforementioned sinusoidal-cosine voltage signals. In this context, reference is made to DE 10 2022 207 258 A1, which was already mentioned at the beginning and in which such a concept is disclosed by way of example, according to which a parking lock or locking device is integrated into the electric motor drive unit 4 and is received by a housing of the electric motor, wherein in turn a rotor position sensor RPS is integrated into the parking lock. Reference is made to the printed circuit board (PCB) described in this application as part of the parking lock control unit. This PCB features control electronics with an integrated signal generator containing a coil assembly, which interacts with a sensor component in the form of a metallic, disc-like element that is stationary relative to the rotor shaft of the electric motor. This metallic element functions as a sensor wheel, which, in conjunction with the signal generator, produces the aforementioned sinusoidal voltage signals. The PCB may include a processing unit that calculates the vehicle speed from these sinusoidal voltage signals. In the proposed method for actuating the vehicle's parking lock, the parking lock is actuated to lock or block the drivetrain when a definable reference speed of the vehicle is undershot by a vehicle speed determined based on the said sinusoidal-cosine voltage signals. The control units described above comprise a digital microprocessor unit (CPU) connected to a memory system and a bus system, a working memory (RAM), and a storage medium. The CPU is configured to execute instructions stored as a program in a memory system, to acquire input signals from the data bus, and to output signals to the data bus. The memory system can utilize various storage media, including magnetic, solid-state, and other non-volatile media, on which a corresponding computer program for carrying out the process and its advantageous embodiments is stored. The program can be designed to embody or execute the process aspects described herein, enabling the CPU to perform the steps of such processes and thus control both the vehicle and the parking lock or locking device. A computer program suitable for carrying out the method is one which has program code means to perform all steps of any one of the claims or method claims when the program is executed in the CPU. The computer program can be easily integrated into existing control electronics and used to control both the vehicle and the parking lock or locking device. This includes a computer program product with program code stored on a computer-readable data carrier to perform the method according to any one 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. Although the preceding description explains exemplary embodiments, it should be noted that a multitude of variations are possible. Furthermore, it should be emphasized that the exemplary embodiments are merely examples and are not intended to restrict the scope of protection, applications, or structure in any way. Rather, the preceding description provides the skilled person with a guideline 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 defined by the claims and these equivalent combinations of features.

Claims

Method for actuating a parking lock of an electric motor for driving a vehicle, wherein the parking lock is received by a housing of the electric motor and actuated when a defined reference speed of the vehicle is undershot by a determined vehicle speed, wherein the vehicle speed is determined by means of a rotor position sensor (RPS) integrated into the parking lock, which provides periodic voltage signals for determining the vehicle speed within a control unit of the vehicle. Method according to claim 1, wherein the vehicle speed determined in this way is used to verify the plausibility of vehicle speed guidance information determined on the basis of other sensor signals. Method according to claim 1, wherein the vehicle speed thus determined is used as vehicle speed guidance information. Method according to one of the preceding claims, wherein the vehicle speed thus determined is determined within a control unit integrated into the parking lock. Computer program for carrying out a method according to any one of the preceding claims 1 to 4. 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 4 when the program code means are executed on a computer. Vehicle with a computer program according to claim 5 or a computer program product according to claim 6. Use of a rotor position sensor (RPS) integrated into a parking lock of an electric motor of an electric motor drive unit for propelling a vehicle for actuating the parking lock, wherein the parking lock is received by a housing of the electric motor, wherein a vehicle speed is determined within a control unit of the vehicle for releasing a locking request based on periodic voltage signals provided by the rotor position sensor (RPS).

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